Fc receptor binding proteins

ABSTRACT

This disclosure provides, inter alia, proteins that bind to FcRn, e.g., immunoglobulins that inhibit FcRn with high affinity and selectivity. The FcRn-binding proteins can be used to treat a variety of disorders including autoimmune disorders.

RELATED APPLICATIONS

This is a Divisional of application Ser. No. 14/168,839, filed Jan. 30,2014, which is a divisional of application Ser. No. 13/617,498 filedSep. 14, 2012 (now U.S. Pat. No. 8,815,246 issued Aug. 26, 2014); whichis a divisional of application Ser. No. 12/429,529 filed Apr. 24, 2009(now U.S. Pat. No. 8,273,351 issued Sep. 25, 2012), which claimspriority to Provisional Application No. 61/048,152 filed Apr. 25, 2008and Provisional Application No. 61/048,500 filed Apr. 28, 2008.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted in ASCII format via EFS-Web and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Dec. 22, 2015, isnamed 208062_0001_04_ST25.txt and is 115,725 bytes in size.

BACKGROUND

The most abundant antibody isotype in the serum is IgG and it has acritical role in mediating protection against pathogens as well as inmediating allergic and inflammatory responses that hasten recruitment ofimmune system components to the tissues, mucosae, and dermal surfaces(Junghans, Immunologic Research 16(1):29 (1997)). Moreover, it is also akey component of a variety of autoimmune diseases. Under normalconditions, the half-life of IgG in the serum is in the range of 5-7days in mice and 22-23 days in humans, which is a prolonged period,relative to the serum half life of other plasma proteins. In part, thisoccurs because the neonatal FcRn receptor (FcRn) rescues pinocytosed IgGfrom degradative lysosomes and recycles it back to the extracellularcompartment (Junghans and Anderson, Proc. Natl. Acad. Sci. USA 93:5512(1996), Roopenian et al. J. Immunology 170:3528 (2003)).

FcRn binds to the Fc portion of IgG. The interaction between the IgG Fcregion and FcRn is pH-dependent. Upon entry into cells by fluid phaseendocytosis, IgG is sequestered into endosomes and binds to FcRn withhigh affinity at acidic pH (6-6.5); when the IgG-FcRn complex cycles tothe plasma membrane, IgG dissociates rapidly from FcRn in thebloodstream at slightly basic pH (˜7.4). By this receptor-mediatedrecycling mechanism, FcRn effectively rescues the IgG from degradationin lysosomes, thereby prolonging the half-life of 84618601.1 circulatingIgG.

FcRn is a non-covalent heterodimer that typically resides in theendosomes of endothelial and epithelial cells. It is a membrane boundreceptor with a single-pass transmembrane having three heavy chain alphadomains (α1, α2, and α3) and a single soluble light chainβ2-microglobulin (β2M) domain. Structurally, it belongs to a family ofmajor histocompatibility complex class 1 molecules that have β2M as acommon light chain. The FcRn a chain is a 46 kD protein composed of anextracellular domain containing the α1, α2, and α3 heavy chain domains,a transmembrane region, and a relatively short cytoplasmic tail(Burmeister et al. Nature 372:366 (1994)).

FcRn was first identified in the neonatal rat gut, where it functions tomediate the absorption of IgG antibody from the mother's milk andfacilitates its transport to the circulatory system (Leach et al. JImmunol 157:3317 (1996)). FcRn has also been isolated from humanplacenta, where it also mediates absorption and transport of maternalIgG to the fetal circulation. In adults, FcRn is expressed in a numberof tissues, including epithelial tissues of the lung, intestine, kidney,as well as nasal, vaginal, and biliary tress surfaces (U.S. Pat. Nos.6,030,613 and 6,086,875; Israel et al. Immunology 92:69 (1997);Kobayashi et al. Am J Physiol (2002); Renal Physiol 282:F358 (2002)).

In order to study the contributions of FcRn to IgG homeostasis, micehave been engineered so that at least part of the genes encoding β2M andFcRn heavy chains have been “knocked out” so that these proteins are notexpressed (WO 02/43658; Junghans and Anderson, Proc Natl Acad Sci US93:5512 (1996)). In these mice, the serum half-life and concentrationsof IgG were dramatically reduced, suggesting a FcRn dependent mechanismfor IgG homeostasis.

It has also been suggested that anti-human FcRn antibodies may begenerated in these FcRn knockout mice and that these antibodies mayprevent the binding of IgG to FcRn. However, such antibodies have notbeen generated or tested (WO 02/43658).

The inhibition of IgG binding to FcRn negatively alters IgG serumhalf-life by preventing IgG recycling. This principle has been shown tobe therapeutically effective in a mouse model of autoimmune cutaneousbullous diseases (Li et al. J Clin Invest 115:3440-3450 (2005)).Accordingly, agents that block or antagonize the binding of IgG to FcRnmay be used in a method to treat or prevent autoimmune and inflammatorydiseases or disorders characterized by the presence of inappropriatelyregulated IgG antibodies.

SUMMARY

This invention relates, inter alia, to antibodies that bind FcRn, andmethods of identifying and using such antibodies.

In one aspect the invention provides an isolated antibody comprising aheavy chain (HC) immunoglobulin variable domain sequence and a lightchain (LC) immunoglobulin variable domain sequence,

wherein the heavy chain and light chain immunoglobulin variable domainsequences form an antigen binding site that binds to human FcRn; andwherein the antibody includes one or more of the followingcharacteristics:

-   -   (a) a human CDR or human framework region;    -   (b) the LC immunoglobulin variable domain sequence comprises one        or more CDRs that are at least 85% identical to a CDR of a LC        variable domain of M0171-A03, M0171-A01, M0159-A07, M0161-B04,        M0090-F11 or DX2500;    -   (c) the HC immunoglobulin variable domain sequence comprises one        or more CDRs that are at least 85% identical to a CDR of a HC        variable domain of M0171-A03, M0171-A01, M0159-A07, M0161-B04,        M0090-F11 or DX2500;    -   (d) the LC immunoglobulin variable domain sequence is at least        85% identical to a LC variable domain of M0171-A03, M0171-A01,        M0159-A07, M0161-B04, M0090-F11 or DX2500;    -   (e) the HC immunoglobulin variable domain sequence is at least        85% identical to a HC variable domain of M0171-A03, M0171-A01,        M0159-A07, M0161-B04 M0090-F11 or DX2500; and    -   (f) the antibody binds an epitope that overlaps with an epitope        bound by M0171-A03, M0171-A01, M0159-A07, M0161-B04, M0090-F11        or DX2500.

In one aspect the invention provides an isolated antibody that is atleast 85% identical to an antibody selected from the group consisting ofM0171-A03, M0171-A01, M0159-A07, M0161-B04, M0090-F11 and DX2500.

In one aspect the invention provides an isolated antibody selected fromthe group consisting of M0171-A03, M0171-A01, M0159-A07, M0161-B04,M0090-F11 and DX2504.

In one aspect the invention provides an isolated antibody comprising theCDRs of M0161-B04. In one aspect the invention provides an isolatedantibody that is at least 85% identical to M0161-B04. The CDRs ofM0161-B04 are represented in Table 17A.

In one aspect the invention provides an isolated antibody comprising theCDRs of M0171-A03. In one aspect the invention provides an isolatedantibody that is at least 85% identical to M0171-A03. The CDRs ofM0171-A03 are represented in Table 17A.

In one aspect the invention provides an isolated antibody comprising theCDRs of M0171-A01. In one aspect the invention provides an isolatedantibody that is at least 85% identical to M0171-A01. The CDRs ofM0171-A01 are represented in Table 17A.

In one aspect the invention provides an isolated antibody comprising theCDRs of M0159-A07. In one aspect the invention provides an isolatedantibody that is at least 85% identical to M0159-A07. The CDRs ofM0159-A07 are represented in Table 17A.

In one aspect the invention provides an isolated antibody comprising theCDRs of M0090-F11. In one aspect the invention provides an isolatedantibody that is at least 85% identical to M0090-F11. The CDRs ofM0090-F11 are represented in Table 17A.

In one aspect the invention provides an isolated antibody comprising theCDRs of DX-2500. In one aspect the invention provides an isolatedantibody that is at least 85% identical to DX-2500. The CDRs of DX-2500are represented in Table 17A.

In some embodiments of the antibodies provided herein the HC variabledomain sequence comprises a variable domain sequence of M0161-B04 andthe LC variable domain sequence comprises a variable domain sequence ofM0161-B04.

In some embodiments of the antibodies provided herein the HC variabledomain sequence comprises a variable domain sequence of M0171-A03 andthe LC variable domain sequence comprises a variable domain sequence ofM0171-A03.

In some embodiments of the antibodies provided herein the HC variabledomain sequence comprises a variable domain sequence of M0171-A01 andthe LC variable domain sequence comprises a variable domain sequence ofM0171-A01.

In some embodiments of the antibodies provided herein the HC variabledomain sequence comprises a variable domain sequence of M0159-A07 andthe LC variable domain sequence comprises a variable domain sequence ofM0159-A07.

In some embodiments of the antibodies provided herein the HC variabledomain sequence comprises a variable domain sequence of M0090-F11 andthe LC variable domain sequence comprises a variable domain sequence ofM0090-F11.

In some embodiments of the antibodies provided herein the HC variabledomain sequence comprises a variable domain sequence of DX2500 and theLC variable domain sequence comprises a variable domain sequence ofDX2500.

In some embodiments of the antibodies provided herein the antibody bindsto an FcRn epitope bound by M0171-A03, M0171-A01, M0159-A07, M0161-B04,M0090-F11 or DX2500.

In some embodiments of the antibodies provided herein the antibodycompetes with M0171-A03, M0171-A01, M0159-A07, M0161-B04, M0090-F11 orDX2500 for binding to FcRn.

As used herein M0171-A03 is also referred to as M171-A03 and M00171-A03.As used herein M0171-A01 is also referred to as M171-A01 and M00171-A01.As used herein M0159-A07 is also referred to as M159-A07 and M00159-A07.As used herein M0161-B04 is also referred to as M161-B04, M00161-B04 andDX-2504. As used herein M0090-F11 is also referred to as M090-F11 andM90-F11.

In one aspect the invention provides an isolated antibody, or a fragmentthereof, which binds to human FcRn, wherein the antibody is generatedagainst the heavy chain of human FcRn or a fragment thereof, wherein theantibody functions as a non-competitive inhibitor of IgG binding tohuman FcRn, and wherein the antibody does not bind β2-microglobulin.

In one aspect the invention provides an isolated antibody, or fragmentthereof, that binds to human FcRn, wherein the antibody is generatedagainst the heavy chain of human FcRn or a fragment thereof, wherein theantibody does not bind β2-microglobulin when it is not complexed withFcRn, and wherein the antibody is not produced from a FcRn −/− knockoutmouse.

In some of the embodiments of the antibodies provided herein theantibody is selected from the group consisting of 3B3.11, 31.1, 4B4.12,and 17D3.

In some of the embodiments of the antibodies provided herein theantibody binds human FcRn at about pH range 5-7.4 with a dissociationconstant (K_(D)) of less than 100 nM.

In some of the embodiments of the antibodies provided herein the antigenbinding site specifically binds to human FcRn.

In some of the embodiments of the antibodies provided herein theantibody binds a stable FcRn expressing cell line.

In some of the embodiments of the antibodies provided herein theantibody modulates (e.g., inhibits) FcRn binding to anantibody/immunoglobulin constant region.

In some of the embodiments of the antibodies provided herein theantibody binds to the alpha subunit of FcRn.

In some of the embodiments of the antibodies provided herein theantibody binds the α1, α2, or α3 domain of the FcRn alpha chain.

In some of the embodiments of the antibodies provided herein theantibody does not bind a beta subunit of FcRn, i.e., the protein onlybinds an alpha subunit.

In some of the embodiments of the antibodies provided herein theantibody binds to a beta subunit of FcRn, wherein the beta subunit isassociated with an alpha subunit.

In some of the embodiments of the antibodies provided herein the alphaand beta subunit are correctly assembled into FcRn.

In some of the embodiments of the antibodies provided herein theantibody binds an FcRn that contains both an alpha subunit and a betasubunit and is correctly assembled.

In some of the embodiments of the antibodies provided herein theantibody inhibits the binding of IgG-Fc with an IC₅₀ of less than about800 nM, less than about 600 nM, less than about 300 nM, less than about100 nM, less than about 50, nM, less than about 25 nM, less than about10 nM, or less than about 5 nM at about pH 6.

In some of the embodiments of the antibodies provided herein theantibody is soluble Fab.

In some of the embodiments of the antibodies provided herein theantibody binds to FcRn through its antigen binding domain and alsothrough its Fc region.

In some of the embodiments of the antibodies provided herein the bindingof the antibody to FcRn is substantially pH independent in the range of2-10.

In some of the embodiments of the antibodies provided herein the bindingof the antibody to FcRn is substantially pH independent in the range of6-8.

In some of the embodiments of the antibodies provided herein theantibody has a k_(off) of less than 0.01, 0.001, 0.0001, 0.00001 s⁻¹ atpH 7.5.

In some of the embodiments of the antibodies provided herein the bindingof the antibody to FcRn is substantially pH dependent.

In some of the embodiments of the antibodies provided herein theantibody preferentially binds human FcRn as compared to rat FcRn in apH-dependent or pH-independent manner.

In some of the embodiments of the antibodies provided herein theantibody binds FcRn in endosomes or under endosomal conditions.

In some of the embodiments of the antibodies provided herein theantibody does not release FcRn at pH 7.5.

In some of the embodiments of the antibodies provided herein theantibody causes an amelioration of symptoms associated with anautoimmune disorder when administered to a subject.

In some of the embodiments of the antibodies provided herein the HC andLC variable domain sequences are components of the same polypeptidechain.

In some of the embodiments of the antibodies provided herein the HC andLC variable domain sequences are components of different polypeptidechains.

In some of the embodiments of the antibodies provided herein theantibody is a full-length antibody.

In some of the embodiments of the antibodies provided herein theantibody is a human or humanized antibody or is non-immunogenic in ahuman.

In some of the embodiments of the antibodies provided herein theantibody comprises a human antibody framework region.

In some of the embodiments of the antibodies provided herein theantibody comprises an Fc domain.

In some of the embodiments of the antibodies provided herein theantibody is a murine antibody.

In some of the embodiments of the antibodies provided herein theantibody is a monoclonal antibody.

In some of the embodiments of the antibodies provided herein theantibody is chimeric or humanized.

In some of the embodiments of the antibodies provided herein theantibody is selected from the group consisting of Fab, F(ab)′2, Fv andScFv.

In some of the embodiments of the antibodies provided herein theantibody binding to FcRn is independent of the pH over a pH range of 6.0to 8.0.

In one aspect the invention provides a pharmaceutical compositioncomprising the any one of the antibodies provided herein and apharmaceutically acceptable carrier.

In one aspect the invention provides an isolated nucleic acid comprisinga sequence that encodes a polypeptide that includes a sequence at least80% identical to the sequence of a variable domain of M0171-A03,M0171-A01, M0159-A07 or M0161-B04.

In one aspect the invention provides an isolated nucleic acid comprisinga sequence that encodes a polypeptide comprising the first and/or thesecond immunoglobulin variable domain of the any one of the antibodiesprovided herein.

In one aspect the invention provides a vector or host cell comprisingthe nucleic acid sequence provided herein

In one aspect the invention provides a method of detecting an FcRn in asample, the method comprising: contacting the sample with any one of theantibodies provided herein and detecting an interaction between theantibody and the FcRn if present. In some embodiments the antibodyfurther comprises a detectable label.

In one aspect the invention provides a method of detecting FcRn in asubject, the method comprising: administering any one of the antibodiesprovided herein that further comprises a detectable label, to a subject;and detecting the label in the subject. In some embodiments detectingcomprises imaging the subject.

In one aspect the invention provides a method of modulating an FcRnactivity, the method comprising: contacting an FcRn with any one of theantibodies provided herein, thereby modulating the activity of the FcRn.In some embodiments the FcRn is in a human subject. In some embodimentsthe antibody prevents binding of the FcRn to an endogenous Ig.

In some embodiments the antibody prevents binding of the FcRn to atherapeutic antibody. In some embodiments the FcRn is in an epithelialcell endosome. In some embodiments the FcRn is in an endothelial cellendosome. In some embodiments the FcRn is on the cell surface.

In one aspect the invention provides a method of treating an autoimmunedisorder and/or modulating symptoms of an autoimmune disorder, themethod comprising: administering any one of the antibodies providedherein in an amount sufficient to modulate the symptoms. In someembodiments the autoimmune disorder is a disorder selected from thegroup consisting of: rheumatoid arthritis (RA), systemic lupuserythematosus (SLE), Myasthenia Gravis (MG), Graves Disease, IdiopathicThrombocytopenia Purpura (ITP), Guillain-Barre Syndrome, autoimmunemyocarditis, Membrane Glomerulonephritis, diabetes mellitus, Type I orType II diabetes, multiple sclerosis, Raynaud's syndrome, autoimmunethyroiditis, gastritis, Celiac Disease, Vitiligo, Hepatitis, primarybiliary cirrhosis, inflammatory bowel disease, spondyloarthropathies,experimental autoimmune encephalomyelitis, immune neutropenia, juvenileonset diabetes, and immune responses associated with delayedhypersensitivity mediated by cytokines, T-lymphocytes typically found intuberculosis, sarcoidosis, and polymyositis, polyarteritis, cutaneousvasculitis, pemphigus, pemphigoid, Goodpasture's syndrome, Kawasaki'sdisease, systemic sclerosis, anti-phospholipid syndrome, and Sjogren'ssyndrome. In some embodiments the pemphigus is pemphigus vulgaris,pemphigus foliaceus or paraneoplastic pemphigus. In some embodiments theantibody decreases the half-life of endogenous IgG.

In one aspect the invention provides a method of modulating thehalf-life of circulating IgG, the method comprising: identifying asubject in need of modulated circulating IgG half-life/levels; andadministering the antibody of any one of the antibodies provided hereinto the subject in amount effective to modulate the half-life/levels ofcirculating IgG in the subject. In some embodiments the method reducescirculating IgG half-life/levels. In some embodiments the subject is ahuman. In some embodiments the antibody is administered to decrease thehalf-life/levels of circulating IgG and in combination with ananti-autoimmune disorder agent or therapy that is not any one of theantibodies provided herein. In some embodiments the anti-autoimmunedisorder agent or therapy that is not any one of the antibodies providedherein comprises intravenous Ig therapy; nonsteroidal anti-inflammatorydrugs (NSAID); corticosteroids; cyclosporins, rapamycins, ascomycins, ortheir immunosuppressive analogs, e.g., cyclosporin A, cyclosporin G,FK-506, rapamycin, 40-O-(2-hydroxy)ethyl-rapamycin; cyclophosphamide;azathioprene; methotrexate; brequinar; FTY 720; leflunomide;mnizoribine; mycophenolic acid; mycophenolate mofetil;15-deoxyspergualine; immunosuppressive monoclonal antibodies, e.g.,monoclonal antibodies to leukocyte receptors, e.g., MHC, CD2, CD3, CD4,CD7, CD25, CD28, B7, CD45, or CD58 or their ligands; otherimmunomodulatory compounds, e.g. CTLA4Ig; or other adhesion moleculeinhibitors, e.g., mAbs or low molecular weight inhibitors includingselectin antagonists and VLA-4 antagonists.

In one aspect the invention provides a method of treating or preventingan autoimmune disorder, the method comprising: administering any one ofthe antibodies provided herein to a subject having the disorder or atrisk of developing the disorder. In some embodiments the autoimmunedisorder is characterized by unwanted circulating IgG. In someembodiments the antibody decreases the half-life of endogenous IgG. Insome embodiments the autoimmune disorder is a disorder selected fromrheumatoid arthritis (RA), systemic lupus erythematosus (SLE),Myasthenia Gravis (MG), Graves Disease, Idiopathic ThrombocytopeniaPurpura (ITP), Guillain-Barre Syndrome, autoimmune myocarditis, MembraneGlomerulonephritis, diabetes mellitus, Type I or Type II diabetes,multiple sclerosis, Raynaud's syndrome, autoimmune thyroiditis,gastritis, Celiac Disease, Vitiligo, Hepatitis, primary biliarycirrhosis, inflammatory bowel disease, spondyloarthropathies,experimental autoimmune encephalomyelitis, immune neutropenia, juvenileonset diabetes, and immune responses associated with delayedhypersensitivity mediated by cytokines, T-lymphocytes typically found intuberculosis, sarcoidosis, and polymyositis, polyarteritis, cutaneousvasculitis, pemphigus, pemphigoid, Goodpasture's syndrome, Kawasaki'sdisease, systemic sclerosis, anti-phospholipid syndrome, and Sjogren'ssyndrome. In some embodiments the pemphigus is pemphigus vulgaris,pemphigus foliaceus or paraneoplastic pemphigus.

In one aspect the invention provides a method of treating or preventingan autoimmune disorder, the method comprising: administering any one ofthe antibodies provided herein, in combination with a second therapy fortreating or preventing the disorder to a subject having the disorder orat risk of developing the disorder. In some embodiments the secondtherapy comprises intravenous Ig therapy; nonsteroidal anti-inflammatorydrugs (NSAID); corticosteroids; cyclosporins, rapamycins, ascomycins, ortheir immunosuppressive analogs, e.g., cyclosporin A, cyclosporin G,FK-506, rapamycin, 40-O-(2-hydroxy)ethyl-rapamycin; cyclophosphamide;azathioprene; methotrexate; brequinar; FTY 720; leflunomide;mnizoribine; mycophenolic acid; mycophenolate mofetil;15-deoxyspergualine; immunosuppressive monoclonal antibodies, e.g.,monoclonal antibodies to leukocyte receptors, e.g., MHC, CD2, CD3, CD4,CD7, CD25, CD28, B7, CD45, or CD58 or their ligands; otherimmunomodulatory compounds, e.g. CTLA4Ig; or other adhesion moleculeinhibitors, e.g., mAbs or low molecular weight inhibitors includingselectin antagonists and VLA-4 antagonists.

In one aspect the invention provides a method of reducing theconcentration of undesired antibodies in an individual comprising thesteps of administrating to the individual a therapeutically effectivedose of any one of the antibodies or antibody fragments provided herein.In some embodiments the antibody or a fragment thereof is administeredin a pharmaceutically acceptable carrier. In some embodiments theindividual is a human. In some embodiments the antibody or fragmentthereof is administered with an adjuvant. In some embodiments theundesired antibody is natalizumab. In some embodiments the undesiredantibody is non-self Human Leukocyte Antigen. In some embodiments theadministered antibody or fragment thereof is administered in connectionwith organ transplant.

In one aspect the invention provides a method of reducing the binding ofIgG to FcRn in an individual comprising the steps of providing anantibody or a fragment thereof which binds to human FcRn, is generatedagainst the heavy chain of human FcRn or a fragment thereof, is anon-competitive inhibitor of IgG binding to human FcRn and does not bindβ2-microglobulin; and administering the antibody or the fragment thereofto an individual in an amount sufficient to reduce the binding of IgG toFcRn in the individual. In some embodiments the individual has anautoimmune or alloimmune disease. In some embodiments the individual isan organ transplant recipient. In some embodiments the individual hasbeen administered a therapeutic antibody. In some embodiments theautoimmune disease is immune thrombocytopenia. In some embodiments theautoimmune disease is immune pemphigus. In some embodiments theindividual is a human. In some embodiments the antibody is administeredat a dosage of 1 mg/kg to 2 g/kg. In some embodiments the antibody isadministered at a dosage of 1 mg/kg to 200 mg/kg.

In one aspect the invention provides a method for suppressing the levelof an IgG antibody in an individual comprising the steps of providing anantibody or a fragment thereof which binds to human FcRn, is generatedagainst the heavy chain of human FcRn or a fragment thereof, is anon-competitive inhibitor of IgG binding to human FcRn and does not bindβ2-microglobulin; and administering the antibody or the fragment thereofto an individual in an amount sufficient to suppress the level of an IgGantibody in an individual. In some embodiments the IgG antibody is atherapeutic IgG antibody. In some embodiments the therapeutic IgGantibody is natalizumab. In some embodiments in the IgG antibody isnon-self Human Leukocyte Antigen. In some embodiments the method furthercomprises a plasma exchange step.

In one aspect, the invention relates to antibodies which inhibit theconstant region of an IgG molecule from binding to FcRn. The inventionthus relates to an antibody comprising at least one variable region thatspecifically binds a FcRn molecule epitope. In some embodiments, theantibodies of the invention bind to human FcRn. In other embodiments,the antibodies bind to rodent or monkey FcRn. Some exemplary antibodiesof the invention include, e.g., 4B4.12, 3B3.11, 31.1, and 17D3.

In one aspect, the disclosure features an antibody (e.g., an isolatedantibody) that includes a heavy chain (HC) immunoglobulin variabledomain sequence and a light chain (LC) immunoglobulin variable domainsequence. The first and second immunoglobulin variable domain sequencesform an antigen binding site that binds to FcRn (e.g., human FcRn). Inone embodiment, the antibody has one or more of the followingcharacteristics:

-   -   (a) the LC immunoglobulin variable domain sequence is at least        85% identical to a LC variable domain of 3B3.11, 31.1,        532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11, M0092-D02,        M0055-G12, M0057-F02, M0062-009, M0064-H04, M0073-E10, or        M0090-F11, or one or more CDRs thereof;

(b) the HC immunoglobulin variable domain sequence is at least 85%identical to a HC variable domain of 3B3.11, 31.1, 532A-M0090-F09,M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02,M0062-009, M0064-H04, M0073-E10, or M0090-F11, or one or more CDRsthereof; and

-   -   (c) the antibody binds an epitope that overlaps with an epitope        bound by 3B3.11, 31.1, 532A-M0090-F09, M0084-B03, M0056-G05,        M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009,        M0064-H04, M0073-E10, or M0090-F11.

In one embodiment, the antibody binds FcRn (e.g., human FcRn), e.g., inabout pH range 5-8, e.g., with a dissociation constant (K_(D)) of lessthan 100, 50, 10, 5, 1, or 0.1 nM. In one embodiment, the antigenbinding site specifically binds to human FcRn. As used herein, “specificbinding” or “specifically binds” refers to the ability of a FcRn bindingantibody to preferentially bind to human FcRn, with an affinity that isat least two-fold, 10-fold, 50-fold, 100-fold, or better (smaller K_(D))than its affinity for binding to a non-specific antigen (e.g., actin,casein) other than FcRn. In one embodiment, the antibody binds humanFcRn with a k_(off) of less than 0.01, 0.001, 0.0001, 0.00001 s⁻¹.

In one embodiment, the antibody binds the extracellular domain of FcRn;for example, one of the alpha subunits of FcRn, i.e., the α1, α2, or α3domain of the FcRn alpha chain. In one embodiment, the antibody does notbind the beta β2M) subunit of FcRn, e.g., the antibody binds only thealpha subunit. In one embodiment, the antibody does bind to the betasubunit of FcRn, but, only when β2M is in association with the alphasubunit. For example, the antibody does not bind to either alpha or betasubunit unless both are present and correctly assembled into FcRn. Inone embodiment, the antibody binds to the FcRn that contains both thealpha and beta subunits and is correctly assembled.

In one embodiment, the antibody modulates (e.g., inhibits) FcRn bindingto an antibody/immunoglobulin constant region. For example, the antibodycan have a K_(i) of better than (e.g., numerically less than) 5 nM, 500pM, 200 pM, 150 pM, 100 pM, or 75 pM, e.g., between 50 nM and 1 pM, or200 pM and 5 pM.

In one embodiment, the antibody binds to FcRn and decreases or preventsFcRn binding to an antibody/immunoglobulin constant region. For example,the antibody can bind to FcRn (e.g., human FcRn) with an affinity(K_(D)) of better than (i.e., numerically smaller than) 1×10⁻⁸ M. In oneembodiment, the antibody is a Fab that binds to FcRn in a substantiallypH independent or substantially pH dependent manner and with a K_(D) inthe range of about 3.0-82 nM at pH 6. In one embodiment, the antibody isa Fab that binds to FcRn in a substantially pH independent orsubstantially pH dependent manner and with a K_(D) in the range of about9.7-about 39.7 nM at pH 7.5. In one embodiment, the antibody is an IgGthat binds to FcRn in a substantially pH independent or substantially pHdependent manner and with a K_(D) in the range of about 0.409-about 29.5nM, about 2.44-about 29.5 nM, about 0.13-about 1.03 nM, about 6.43-about30.2 nM, about 0.2-about 2.87 nM, about 0.34-about 2.87 nM, or about0.2-about 30.2 nM at pH 6. In one embodiment, the antibody is an IgGthat binds to FcRn in a substantially pH independent or substantially pHdependent manner and with a K_(D) in the range of about 0.675-24.2 nM,2.1-24.2 nM, 0.158-10 nM, or about 2.04-about 80 nM at pH 7.5.

In one embodiment, the antibody inhibits the binding of FcRn to IgG-Fcwith an IC₅₀ of less than 800 nM, 600 nM, or 300 nM, 200 nM, 100 nM, 1nM, 50 pM at about pH 6. In one embodiment, the antibody is a Fab thatinhibits the binding of FcRn to IgG-Fc in a substantially pH independentor substantially pH dependent manner and with an IC₅₀ in the range ofabout 13-754 nM or about 13-80 nM at pH 6. In one embodiment, theantibody is an IgG that inhibits the binding of FcRn in a substantiallypH independent or substantially pH dependent manner and with an IC₅₀ inthe range of about 1.2-36 nM, 36-120 nM, 120-562 nM, 1.5-5.4 nM, 5.4-50nM, 51-161 nM at pH 6.

In one embodiment, the antibody is, e.g., a single chain antibody, aFab, an sFab fragment, an F(ab′)2, an Fd fragment, an Fv fragment, anscFv, or a dAb fragment.

In some embodiments, the antibody monospecific, e.g., a monoclonalantibody or recombinant antibody. The term “monospecific antibody”refers to an antibody that displays a single binding specificity andaffinity for a particular target, e.g., epitope. This term includes a“monoclonal antibody” or “monoclonal antibody composition,” which asused herein refer to a preparation of an antibody of a single molecularcomposition.

In one embodiment, the antibody is a recombinant or modified anti-FcRnantibody, e.g., a chimeric, a humanized, a deimmunized, or an in vitrogenerated antibody. The term “recombinant” or “modified” human antibody,as used herein, is intended to include all antibodies that are prepared,expressed, created or isolated by recombinant means, such as antibodiesexpressed using a recombinant expression vector transfected into a hostcell, antibodies isolated from a recombinant, combinatorial antibodylibrary, antibodies isolated from an animal (e.g., a mouse) that istransgenic for human immunoglobulin genes or antibodies prepared,expressed, created or isolated by any other means that involves splicingof human immunoglobulin gene sequences to other DNA sequences. Suchrecombinant antibodies include humanized, CDR grafted, chimeric,deimmunized, in vitro generated antibodies, and may optionally includeconstant regions derived from human germline immunoglobulin sequences.In one embodiment, the antibody does not elicit an anti-globulinresponse in a human.

Also disclosed are antibodies (including full length antibodies orantigen-binding fragments thereof) that bind overlapping epitopes of, orcompetitively inhibit, the binding of the anti-FcRn antibodies disclosedherein to FcRn e.g., antibodies which bind overlapping epitopes of, orcompetitively inhibit, the binding of sFabs 532A-M0090-F09, M0084-B03,M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009,M0064-H04, M0073-E10, or M0090-F11 to FcRn. It is also possible to use acombination of anti-FcRn antibodies, e.g., two or more antibodies thatbind to different regions of FcRn, e.g., antibodies that bind to twodifferent epitopes on the extracellular domain of FcRn. Alternatively, abispecific antibody can be used. A bispecific antibody is a moleculewith two variable heavy and two variable light domains so that thesingle molecule embodies two specific binding capabilities; one or moreof the variable domains or specificities can be of an antibody describedherein and bind to FcRn.

In one embodiment, the anti-FcRn antibody (e.g., a full length antibodyor antigen-binding fragment thereof) includes at least one light orheavy chain variable domain sequence (e.g., at least one light chainimmunoglobulin and at least one heavy chain immunoglobulin). In someembodiments, each immunoglobulin includes a light or a heavy chainvariable domain sequence having at least one, two or threecomplementarity determining regions (CDR's) substantially identical to aCDR from a light or heavy chain variable domain sequence of an antibodythat interacts with FcRn, e.g., an sFab described herein, e.g.,532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12,M0057-F02, M0062-009, M0064-H04, M0073-E10, or M0090-F11.

In one embodiment, the antibody binds to FcRn using its antigen bindingdomain and also through its Fc region. In one embodiment, the antibodybinds to FcRn using only its antigen binding domain. For example, theantibody does not include an Fc region or includes a modified Fc regionthat does not interact with FcRn. In one embodiment, the antibody bindsto FcRn at least 1000-fold more tightly through its antigen-bindingdomains as through its Fc domains.

In one embodiment, the binding of the antibody to FcRn is substantiallypH independent in the range of 2-10, of 4-9, of 5-8, of 6-8, or of6-7.5. The term “pH independent” refers to the ability of the antibodyto bind and/or to remain bound to FcRn at a pH in the range of 2-10,4-9, 5-8, 6-8, or 6-7.5. The affinity may vary at the various pH values.In some embodiments, the K_(D) is no higher than 200 nM, 50 nM, 10 nM, 1nM or 100 pM at any value within the range. For example, the antibodycan bind FcRn at pH 6 and remain bound at pH 7.5. In one embodiment, thebinding of the antibody to FcRn is substantially pH dependent. The term“pH independent” refers to the ability of the antibody to bind/and orremain bound to FcRn at a first pH and the ability to bind or to remainbound to FcRn at a second pH, where the second pH is within a givennumber of pH units (e.g., 6, 5, 4, 3, 2, 1.5 units) of the first pH. Forexample, the antibody can bind FcRn at pH 6 and can also bind or remainbound to FcRn at pH 7.5. The term “pH dependent” refers to the abilityof the antibody to bind/and or remain bound to FcRn at a first pH andthe lack of ability to bind or to remain bound to FcRn at a second pH,where the second pH is within a given number of pH units (e.g., 6, 5, 4,3, 2, 1.5 units) of the first pH. For example, the antibody can bindFcRn at pH 6 and cannot bind or remain bound to FcRn at pH 7.5.

In one embodiment, the antibody preferentially binds human FcRn ascompared to rat or monkey FcRn in a pH-dependent or pH-independentmanner. In one embodiment, the antibody binds both human FcRn and theFcRn of a suitable experimental animal (e.g., rat or monkey) withaffinities that differ by no more than two-, five- or ten-fold. In oneembodiment, the antibody binds both human FcRn and the FcRn of asuitable experimental animal with K_(D)<5 nM in the pH range of 6.0-7.5.In one embodiment, the antibody binds FcRn in endosomes or underendosomal conditions. For example, the antibody binds FcRn under acidicconditions, e.g., pH 6. In one embodiment, the antibody binds FcRn at pH6, e.g., at least 1.5, 2, 5, 8, 10, 20, or 50-fold better than at pH7.5. In one embodiment, the antibody releases FcRn at pH 7.5, e.g., atleast 1.5, 2, 5, 8, 10, 20, or 50-fold more rapidly than at pH 6. In oneembodiment, the antibody binds FcRn at pH 7.5, e.g., at least 1.5, 2, 5,8, 10, 20, or 50-fold better than at pH 6. In one embodiment, theantibody releases FcRn at pH 6, e.g., at least 1.5, 2, 5, 8, 10, 20, or50-fold more rapidly than at pH 7.5. In one embodiment, the antibodydoes not release FcRn at pH 7.5. In one embodiment, the antibody doesnot release FcRn at pH 6.

In one embodiment, the interaction with FcRn extends the half-life ofthe antibody. In one embodiment, the antibody causes the half-life ofother IgG molecules to be diminished, e.g., at least 5, 10, 20, 40, 50,60, 70, 80, or 90%. For example, a reduction of 90% would change thehalf-life of an antibody from 20 days to 2 days.

In one embodiment, the antibody causes an amelioration of symptomsassociated with an autoimmune disorder when administered to a subject.For example, the antibody can alleviate or decrease the severity ofsymptoms such as joint swelling, pain, or stiffness; levels ofcirculating antibodies such as auto-antibodies; achy joints(arthralgia); fever; extreme fatigue; skin rashes; anemia; pain in thechest or deep breathing; butterfly-shaped rash across the cheeks andnose; photosensitivity; hair loss; seizures; mouth or nose ulcers;Raynaud's phenomenon; mild erythema; neuropsychiatric manifestations;thrombocytopenia; and pleural effusion.

In one embodiment, the HC and LC variable domain sequences arecomponents of the same polypeptide chain, that is they are part of asingle-chain antibody. In one embodiment, HC and LC variable domainsequences are components of different polypeptide chains. In oneembodiment, the antibody is a full-length antibody. For example, theantibody can be a human or humanized antibody and/or can benon-immunogenic in a human. In one embodiment, the antibody comprises ahuman antibody framework region. In one embodiment, the antibodycomprises an Fc domain.

In one embodiment, the HC variable domain sequence comprises a variabledomain sequence of 3B3.11, 31.1, 532A-M0090-F09, M0084-B03, M0056-G05,M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009, M0064-H04,M0073-E10, or M0090-F11 and the LC variable domain sequence comprises avariable domain sequence of 3B3.11, 31.1, 532A-M0090-F09, M0084-B03,M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009,M0064-H04, M0073-E10, or M0090-F11. In one embodiment, the antibodybinds to an FcRn epitope bound by 3B3.11, 31.1, 532A-M0090-F09,M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02,M0062-009, M0064-H04, M0073-E10, or M0090-F11. In one embodiment, theantibody competes with 532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11,M0092-D02, M0055-G12, M0057-F02, M0062-009, M0064-H04, M0073-E10, orM0090-F11 for binding to FcRn.

In one aspect, the invention relates to a method of making a monoclonalantibody comprising immunizing a rodent with FcRn protein or at leastone fragment thereof or with a polynucleotide sequence encoding a FcRnmolecule or fragment thereof; obtaining B cells from said rodent; fusingsaid B cells with a myeloma cell line to obtain a hybridoma cell;culturing said hybridoma cell under conditions such that it secretes amonoclonal antibody, wherein said antibody comprises at least onevariable region, which specifically binds to a FcRn molecule, whereinsaid FcRn molecule comprises a domain capable of binding at least aportion of an IgG constant region, wherein the binding of said antibodyto said FcRn molecule inhibits said binding of the portion of an IgGconstant region to said FcRn molecule; and isolating the antibody.

In one aspect, the disclosure features a method of identifying aantibody that binds to FcRn, e.g., human FcRn, and includes: providingan FcRn antigen or a fragment thereof; providing a library ofantibodies, e.g., a display library; and identifying a member present inthe library that binds to the FcRn antigen, where each member of thelibrary displays a heterologous antibody component on its surface andeach member includes a nucleic acid encoding the heterologous antibodycomponent, the heterologous antibody component being a member of a setof diverse antibody components. The method can include isolating anucleic acid molecule from the identified member and the nucleic acidmolecule encodes the polypeptide that specifically binds to the FcRnantigen. In one embodiment, the antibody specifically binds human FcRn.

In one embodiment, the library is a phage library, e.g., a phage displaylibrary. In one embodiment, the identified phage is eluted using acompetitor ligand, e.g., an IgG Fc that binds to FcRn and/or with acompeting anti-human FcRn antibody.

In another aspect, the disclosure features a method of detecting an FcRnin a sample, the method includes: contacting the sample with a FcRnbinding antibody (e.g., a antibody described herein) and detecting aninteraction between the antibody and an FcRn if present.

In one embodiment, the antibody includes a detectable label such as afluorescent tag (e.g. bodipy, fluorecein-5-isothiocyanate, rhodamine,and peroxidase or alkaline phosphatase that are detected in the presenceof chromogenic or chemiluminescent substrates.

In one aspect, the disclosure features a method of modulating an FcRnactivity, the method includes: contacting an FcRn with a FcRn bindingantibody (e.g., a antibody described herein), thereby modulating theactivity (e.g., binding to IgG Fc) of the FcRn. In one embodiment, theFcRn is in a human subject; the FcRn can be in an epithelial orendothelial cell or in the blood (e.g., soluble in the blood or in cellscirculating in the blood) of a human subject. In one embodiment, theantibody prevents binding of the FcRn to a substrate, e.g., anendogenous substrate such as IgG Fc and/or serum albumin. In oneembodiment, the FcRn is in an epithelial or endothelial cell endosome.

In one aspect, the disclosure features a method of treating, preventing,and/or modulating symptoms of a disorder, e.g., an autoimmune disorderor a disorder associated with aberrant FcRn activity. The methodincludes: administering a FcRn binding antibody (e.g., antibodydescribed herein) to a subject, e.g., a subject having the disorder orat risk of developing the disorder. In one embodiment, the ligand isadministered in an amount and/or for a time sufficient to modulate thesymptoms of the disorder.

In one embodiment, the autoimmune disorder is a disorder selected fromthe group consisting of: rheumatoid arthritis (RA), systemic lupuserythematosus (SLE), myasthenia gravis (MG), Graves Disease, idiopathicthrombocytopenia purpura (ITP), Guillain-Barre Syndrome, autoimmunemyocarditis, membrane glomerulonephritis, diabetes mellitus, Type I orType II diabetes, multiple sclerosis, Raynaud's syndrome, autoimmunethyroiditis, gastritis, celiac disease, vitiligo, hepatitis, primarybiliary cirrhosis, inflammatory bowel disease, immune neutropenia,spondyloarthropathies, experimental autoimmune encephalomyelitis,juvenile onset diabetes, and immune responses associated with delayedhypersensitivity mediated by cytokines, T-lymphocytes typically found intuberculosis, sarcoidosis, and polymyositis, polyarteritis, cutaneousvasculitis, pemphigus, pemphigoid, Goodpasture's syndrome, Kawasaki'sdisease, systemic sclerosis, anti-phospholipid syndrome, and Sjogren'ssyndrome.

In one embodiment, the antibodies of the invention may be used toinhibit the transport of IgG across the blood-brain barrier. In anotherembodiment, the antibodies of the invention may be used to treat braintumors or Alzheimer's disease.

In one embodiment, the antibody decreases the half-life of endogenousIgG. In one embodiment, the autoimmune disorder is characterized byunwanted circulating IgG, e.g., unwanted circulating pathogenic IgG.

In one aspect, the disclosure features a method of detecting FcRn in asubject, the method includes: administering a FcRn binding antibody(e.g., antibody described herein) that includes a detectable label, to asubject; and detecting the label in the subject. The method can includeimaging the subject, e.g., using tomography, e.g., MRI.

In one aspect, the disclosure features a method of modulating thehalf-life/levels of circulating IgG, the method includes: identifying asubject, e.g., a human, in need of modulated circulating IgGhalf-life/levels; and administering a FcRn binding antibody (e.g.,antibody described herein) to the subject in amount effective tomodulate the half-life/levels of circulating IgG in the subject. In oneembodiment, the method reduces circulating IgG half-life/levels. In oneembodiment, the antibody is administered to decrease thehalf-life/levels of circulating IgG and in combination with anotheranti-autoimmune disorder agent or therapy. The combination of theadministration of the FcRn antibody and the other anti-autoimmunedisorder agent or therapy may result in a decrease in the level of otheranti-autoimmune disorder agent or therapy needed to modulate or reducethe half-life/levels of circulating IgG.

In another aspect, the disclosure features an isolated nucleic acid thatincludes a first sequence that encodes a first polypeptide that includesa sequence at least 80, 85, 90, 92, 94, 95, 96, 97, 98, 99, or 100%identical to the sequence of a first variable domain sequence of 3B3.11,31.1, 532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11, M0092-D02,M0055-G12, M0057-F02, M0062-009, M0064-H04, M0073-E10, or M0090-F11, ora sequence that hybridizes (e.g., under stringent conditions) to anucleic acid encoding the sequence of a variable domain of 3B3.11, 31.1,532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12,M0057-F02, M0062-009, M0064-H04, M0073-E10, or M0090-F11. In oneembodiment, the nucleic acid further includes a second sequence thatencodes a second polypeptide that includes a second variable domainsequence (of a corresponding variable domain), e.g., a sequence at least80, 85, 90, 92, 94, 95, 96, 97, 98, 99, or 100% identical to thesequence of a second variable domain sequence of 3B3.11, 31.1,532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12,M0057-F02, M0062-009, M0064-H04, M0073-E10, or M0090-F11, or a sequencethat hybridizes (e.g., under stringent conditions) to a nucleic acidencoding the sequence of a variable domain of 3B3.11, 31.1,532A-M0090-F09, M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12,M0057-F02, M0062-009, M0064-H04, M0073-E10, or M0090-F11. In oneembodiment, the nucleic acid further includes regulatory sequences(e.g., a promoter sequence, an untranslated 5′ region, and anuntranslated 3′ region) and/or vector sequences. For example, thenucleic acid constitutes a vector.

In still another aspect, the disclosure features a host cell that canexpress an antibody. The host cell includes one or more nucleic acidsthat collectively include: (1) a first sequence that encodes a firstvariable domain sequence that includes a sequence at least 80, 85, 90,92, 94, 95, 96, 97, 98, 99, or 100% identical to the sequence of a firstvariable domain sequence of 3B3.11, 31.1, 532A-M0090-F09, M0084-B03,M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009,M0064-H04, M0073-E10, or M0090-F11, or a sequence that hybridizes (e.g.,under stringent conditions) to a nucleic acid encoding the sequence of avariable domain of 3B3.11, 31.1, 532A-M0090-F09, M0084-B03, M0056-G05,M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009, M0064-H04,M0073-E10, or M0090-F11 and (2) a second sequence that encodes a secondvariable domain sequence that includes a second variable domain sequence(of a corresponding variable domain), e.g., a sequence at least 80, 85,90, 92, 94, 95, 96, 97, 98, 99, or 100% identical to the sequence of asecond variable domain sequence of 3B3.11, 31.1, 532A-M0090-F09,M0084-B03, M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02,M0062-009, M0064-H04, M0073-E10, or M0090-F11, or a sequence thathybridizes (e.g., under stringent conditions) to a nucleic acid encodingthe sequence of a variable domain of 532A-M0090-F09, M0084-B03,M0056-G05, M0084-B11, M0092-D02, M0055-G12, M0057-F02, M0062-009,M0064-H04, M0073-E10, or M0090-F11.

In one aspect, the disclosure features a method of treating orpreventing an autoimmune disorder, the method comprising: administeringa FcRn binding antibody (e.g., a antibody described herein), e.g., incombination with a second therapy, to a subject having an autoimmunedisorder or at risk of developing the disorder. For example, the secondtherapy can be a therapy suitable for treating or preventing thedisorder. In one embodiment, the second therapy can include: intravenousIg therapy; nonsteroidal anti-inflammatory drugs (NSAID);corticosteroids; cyclosporins, rapamycins, ascomycins, or theirimmunosuppressive analogs, e.g. cyclosporin A, cyclosporin G, FK-506,rapamycin, 40-O-(2-hydroxy)ethyl-rapamycin; cyclophosphamide;azathioprine; methotrexate; brequinar; FTY 720; leflunomide; mizoribine;mycophenolic acid; mycophenolate mofetil; 15-deoxyspergualine;immunosuppressive monoclonal antibodies, e.g., monoclonal antibodies toleukocyte receptors, e.g., MHC, CD2, CD3, CD4, CD7, CD25, CD28, B7,CD45, or CD58 or their ligands; other immunomodulatory compounds, e.g.CTLA4Ig; or other adhesion molecule inhibitors, e.g. mAbs or lowmolecular weight inhibitors including selectin antagonists.

In another aspect, the disclosure features a method of treating a fetus,the method includes: conjugating a small molecule or macromoleculardrug, e.g., an antibiotic or vaccine (e.g., viral vaccine), to a FcRnbinding antibody; and administering the conjugate to a pregnant womanwho bears the fetus in utero. In one embodiment, the fetus has adisorder or is at risk for a disorder. Exemplary disorders include animmunological disorder (e.g., an autoimmune disorder, a metabolicdisorder, or an infectious disorder, e.g., a bacterial or viralinfection, e.g., an enteric infection (e.g., Helibacter pyloriinfection).

In another aspect, the disclosure features a method of treating aninfant, the method comprising: conjugating a small molecule ormacromolecular drug to an antibody that binds to FcRn, e.g., a antibodydescribed herein; and introducing the conjugated antibody into breastmilk. The breast milk can be administered to the infant. In oneembodiment, the conjugated antibody is administered to a woman and thewoman is providing breast milk to the infant, directly, e.g., nursing,or indirectly.

Although the invention is discussed primarily in terms of a preferredembodiment of antibodies, one of ordinary skill in the art will readilyrecognize that binding proteins or ligands other than antibodies arewithin the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the result of an ELISA analysis of antibodies in mousesera obtained 56 days after immunization from animals immunized with DNAencoding hFcRn or GPI linked hFcRn; as well as with DNA encoding humanβ2M for reactivity with either hFcRn or human β2M. Mice #180-184 wereimmunized with plasmid encoded hFcRn; Mice #185-189 with plasmid encodedhFcRn and plasmid encoded 1432M; Mice #190-194 were immunized withplasmid encoded GPI-linked hFcRN; Mice #195-199 were immunized withplasmid encoded GPI-linked hFcRn and plasmid encoded 1432M.

FIG. 2 depicts the result of an ELISA analysis of antibodies in mousesera obtained 94 days after immunization from animals immunized with DNAencoding hFcRn or GPI linked hFcRn; as well as with DNA encoding humanβ2M for reactivity with either hFcRn or human β2M.

FIGS. 3A and 3B depict the results of a FACS analysis that was performedto determine whether the supernatants of #182 mouse derived clones werecapable of blocking hIgG binding to hFcRn on 293C11 cells (HEK 293 cellsengineered to overexpress FcRn). 293C11 cells were incubated withhybridoma supernatants for 60-90 minutes then washed with PBS followedby incubation with Alexa fluor-488 labeled hIgG. Results are expressedin terms of either total mean fluorescence intensity (TMFI) or thepercent changed (inhibition or enhancement) in the binding of human IgGto FcRn. FIG. 3A corresponds to clones hIgG1Alex 50 nM, 2B2.18, 17D3.29,4.1, 31.1, 14C5.3, 11.2, 15B6.10, 5A2.15, 3C6.2, 18A3.12, 10B4.2, 5C5.1,6C3.1, 4D4.8, and 7C5.4. FIG. 3B corresponds to clones hIgG1 Alex 50 nM,4.1, 4.14, 4.13, 17D3.1, 17D3.27, 17D3.29, 7C5.4, 7C5.8, and 7C5.1.

FIGS. 4A and 4B depict the results of a FACS analysis that was performedto determine the blocking activity of #187 mouse derived hybridomasupernatants with the method described in Example 6. FIG. 4A expressesthe results in terms of Total mean fluorescence intensity (TMFI). FIG.4B expresses the results in terms of the percent changed (inhibition orenhancement) in the binding of human IgG to FcRn.

FIG. 5A depicts the results of a FACS analysis that was performed todetermine the potency of FcRn blocking activity at variousconcentrations of mAb 31.1, mAb 4.13, and hIgG1. FIG. 5B depicts theresults of a FACS sorting analysis that was performed to determine thepotency of FcRn blocking activity at various concentrations of mAb3B3.11, mAb 4B4.12, and hIgG1. In both FIGS. 5A and 5B, the cell surfacestaining was examined of 293 C11 cells (HEK 293 cells engineered tooverexpress FcRn) that were incubated in the presence ofAlexa-488-labeled hIgG and anti-FcRn blocking monoclonal antibodies orhIgG1. Results are expressed as percentages of hIgG binding to 293C11cells defined as TMFI at various concentration divided by TMFI ofsamples without competitor times 100%).

FIG. 6 depicts the histograms from a FACS analysis that was performed todetermine the binding of mAb 3B3.11, mAb 31.1, mAb 4.13, mAb 4B4.12, andmAb 15B6.1 to the cell surface of hFcRn expressing 293 C11 cells (HEK293 cells engineered to overexpress hFcRn).

FIG. 7 depicts the histograms from a FACS analysis that was performed todetermine the binding of mAb 3B3.11, mAb 31.1, mAb 4.13, and mAb 4B4.12to the cell surface of rat FcRn-expressing cells (rat fibroblastsengineered to overexpress rat FcRn).

FIG. 8 depicts the histograms from a FACS analysis that was performed todetermine the binding of mAb 3B3.11, mAb 4.13, mAb 31.1, mAb 4B4.12, andmAb 15B6.1 to the cell surface of FcRn-expressing mouse 3T3 cells (NIH3T3 cells engineered to overexpress mouse FcRn).

FIG. 9 depicts the histograms from a FACS analysis that was performed todetermine the binding of mAb 3B3.11, mAb 4.13, mAb 31.1, mAb 4B4.12, andmAb 15B6.1 to hFcRn expressed intracellularly in THP cells (a humanmonocytic cell line).

FIG. 10 depicts the histograms from a FACS analysis that was performedto determine the binding of mAb 3B3.11, mAb 4.13, mAb 31.1, mAb 4B4.12,and mAb 15B6.1 to hFcRn expressed intracellularly in Caco-2 cells (ahuman intestinal epithelial cell line).

FIG. 11A depicts the percentage of macrophage population from mousespleen. FIG. 11B depicts the percentage of the total mouse spleen cellpopulation, that are reactive on surface or intracellularly. In bothFIGS. 11A and 11B, either mAb 4B4.12 or the isotype control, mIgG2a(1813) is depicted.

FIG. 12A depicts the average weight of the spleen from mice immunizedwith OVA plus CFA and treated with mAb 4B4.12, the isotype control,mIgG2a (1813) or PBS. FIG. 12B depicts the average weight of theinguinal lymph nodes from mice immunized with OVA plus CFA and treatedwith mAb 4B4.12, the isotype control, mIgG2a (1813) or PBS. Mice wereimmunized with OVA plus CFA and treated IP with 10 injections of 1 mg of4B4.12 or isotype control 1813 for both FIGS. 12A and 12B.

FIG. 13 depicts the effect on serum levels of anti-ovalbumin (OVA) IgGof Balb/c mice, that have been immunized with OVA, and then treated witheither mAb 4B4.12, the positive control, mIgG2a (1813), or PBS. Antibodytreatment consisted of three daily intraperitoneal (IP) injections ofantibodies, followed by 10 antibody injections IP every other day. Theresults shown were obtained after 9 days of antibody treatment (5injections).

FIG. 14 depicts the effect on serum levels of human IgG of CD-1 mice,that have been intraperitoneally (IP) injected with 1 mg/kg of human IgG(Synagis), and then treated 72 hours later by single IP injection ofeither 20 mg/kg of mAb 4B4.12, 20 mg/kg of the isotype control, mIgG2a(1813), or PBS. Serum samples were obtained immediately before mABinjection (72 hr after Synagis injection), 72, and 168 hours after mABinjection. The results shown were obtained from serum taken 24 hoursafter antibody treatment.

FIG. 15 depicts the same experiment as described in FIG. 14 with twoextra serum sampling points (72 and 168 hours). The results wereexpressed as percentage of Synagis remaining when compared to the levelof Synagis before mAB injection.

FIG. 16 depicts a time-course of the effect of treatment with either mAb4B4.12, the isotype control, mIgG2a (1813), or PBS on the severity ofthe symptoms of experimental autoimmune myasthenia gravis (EAMG). Theseverity of the disease was assessed by the assignment of a grade fromzero to four of increasingly severe symptoms as follows: 0, no symptoms;1, weak grip, fatigability and sometimes wheezing; 2, general weakness,hunched posture at rest, decreased body weight, tremors; 3, severeweakness, moribund; and 4, death.

FIG. 17 depicts the effect of treatment with either mAb 4B4.12, theisotype control, mIgG2a (1813), or PBS on weight loss, reported in grams(as depicted on the y-axis) as a result of experimental autoimmunemyasthenia gravis (EAMG).

FIG. 18 depicts a comparison of the clearance kinetics of Biotinylatedhuman IgG (Biotin-hIgG) versus unlabeled human IgG (hIgG) for Tg32B mice(hFcRn+/+, hβ2M+/+, mFcRn−/−, mβ2M−/−). The animals were intravenously(IV) injected with 5 mg/kg of biotinylated human IgG (Synagis) and 495mg/kg of unlabeled hIgG. Sera were collected at the time-points shown inthe figure and serum Biotin-hIgG concentrations were determined usingAvidin plates (Pierce Chemicals) and unlabeled hIgG was measured byELISA.

FIG. 19 depicts the clearance kinetics of Biotinylated human IgG(Biotin-hIgG) for Tg32B mice (hFcRn+/+, hβ2M+/+, mFcRn −/−, mβ2M −/−)following treatment of the animals with mAb 3B3.11. The animals wereintravenously (IV) injected with 5 mg/kg of biotinylated human IgG(Synagis) and 495 mg/kg of unlabeled hIgG. After 24 hours, daily IVinjections of 50 mg/kg of mAb 3B3.11 were initiated and then continuedfor a period of 5 days. Sera were collected at the time-points shown inthe figure and serum Biotin-hIgG concentrations were determined usingAvidin plates (Pierce Chemicals).

FIG. 20 depicts a bar graph from a FACS analysis that was performed todetermine the binding of mAb 3B3.11, mAb 4.13, mAb 31.1, mAb 4B4.12, andmAb 15B6.1 to COS1 cells transfected with monkey FcRn/β2M. The resultsare expressed as TMFI.

FIG. 21 depicts a Western blot that was performed to determine thespecific binding of mAB3B3.11, 15B6.1, 4.13, and 31.1 to hFcRn alphachain and the specific binding of mAb 3B5.4 and 5A4.9 to β2M.

FIG. 22A depicts Biacore epitope analysis that was performed todetermine the epitopes recognized by mAb 3B3.11. FIG. 22B depictsBiacore epitope analysis that was performed to determine the epitopesrecognized by mAB 4.13. FIG. 22C depicts Biacore epitope analysis thatwas performed to determine the epitopes recognized by mAb 31.1. FIG. 22Ddepicts Biacore epitope analysis that was performed to determine theepitopes recognized by mAb 4B4.12.

FIG. 23 depicts the effects of four consecutive daily intravenous dosesof M90-F11, M84-B11 and M55-G12 on Biotin-IgG Catabolism in TG32B mice.

FIG. 24 depicts a dose response of M90-F11 on hIgG catabolism in hFcRnTg mice (four consecutive daily intravenous doses).

FIG. 25 depicts a single dose response of M90-F11 on hIgG catabolism inhFcRn Tg mice.

FIG. 26 depicts approaches used to affinity mature the germlinedM90-F11.

FIG. 27 depicts the effect of affinity matured IgG and soluble FAB inaccelerating the hIgG catabolism in Tg32B mice at a 20 mg/kg IntravenousDose (Biotin IgG & Total IgG).

FIG. 28 depicts the effect of affinity matured IgG and soluble FAB inaccelerating the hIgG catabolism in Tg32B mice at a 5 mg/kg intravenousdose (Biotin IgG & Total IgG).

FIG. 29 depicts M90-F11 germline changes (highlighted in bold)introduced into the light chain but not in the heavy chain.

FIG. 30 depicts allotype variation of IgG.

FIG. 31A depicts the effect of intravenously administered anti-FcRnantibodies on the catabolism of hIgG in Tg32B Mice by measuringconcentration of hIgG in the serum (mg/ml). FIG. 31B depicts the effectof intravenously administered anti-FcRn antibodies on the catabolism ofhIgG Tg32B Mice by measuring % of hIgG serum levels over time (comparedto hIgG serum levels at 24 hours).

FIG. 32 depicts the effect of subcutaneously administered M161-B04(DX2504) anti-FcRn antibody on the catabolism of hIgG in Tg32B Mice.

FIGS. 33A and 33B depict the effect of anti-FcRn antibodies on thecatabolism of hIgG in cynomolgus monkeys. FIG. 33A depicts the times atwhich a blood sample was taken. FIG. 33B depicts the total serum IgGlevel when no anti-FcRn antibody M161-B04 was administered.

FIG. 34A depicts the effect of intravenously administered M161-B04anti-FcRn antibody at 5 mg/kg in monkeys. FIG. 34B depicts the effect ofsubcutaneously administered M161-B04 anti-FcRn antibody at 5 mg/kg inmonkeys. The data for individual monkeys are shown for both FIGS. 34Aand 34B.

FIG. 35A depicts the effect of intravenously administered M161-B04anti-FcRn antibody at 20 mg/kg in monkeys. FIG. 35 B depicts the effectof subcutaneously administered M161-B04 anti-FcRn antibody at 20 mg/kgin monkeys. The data for individual monkeys are shown for both FIGS. 35Aand 35B.

FIG. 36 depicts the effect of intravenously and subcutaneouslyadministered M161-B04 anti-FcRn antibody at various concentrations inmonkeys (data normalized on the pre-dose).

FIG. 37A depicts the effect of intravenously and subcutaneouslyadministered M161-B04 anti-FcRn antibody on the concentration of serumIgA in monkeys (data normalized on the pre-dose). FIG. 37 B depicts theeffect of intravenously and subcutaneously administered M161-B04anti-FcRn antibody on the concentration of serum IgM in monkeys (datanormalized on the pre-dose). FIG. 37C depicts the effect ofintravenously and subcutaneously administered M161-B04 anti-FcRnantibody on the concentration of serum albumin in monkeys (datanormalized on the pre-dose).

FIG. 38 depicts DX-2504 sequences and alignments thereof.

DETAILED DESCRIPTION

In normal circumstances, FcRn can extend the half-life of circulatingIgG. Antibodies that bind to FcRn can be used to modulate FcRn function,for example, by preventing interaction with IgG. In particular,antibodies that block FcRn interaction with IgG can be used to reducethe half-life of IgG molecules.

These antibodies and related strategies can be used to treat and evenprevent antibody-mediated autoimmune disorders such as, multiplesclerosis, inflammatory bowel disease, rheumatoid arthritis (RA), andsystemic lupus erythematosus (SLE), or another autoimmune disorderdescribed herein. An antagonistic anti-rat FcRn monoclonal antibody(mAb)1G3 successfully prevented Experimental Autoimmune MyastheniaGravis (EAMG) in a rat passive model at a dose of 30 mg/kg; that isabout 100 fold lower than the intravenous IgG (WIG) used in treatment ofMG, SLE, and ITP. Further, FcRn-deficient mice genetically predisposedto develop autoimmune disorder such as lupus or arthritis havesignificant reduction in severity of the disease. Thus, anti-human FcRnblocking antibodies have therapeutic potential for treatment ofautoimmune disorders in humans.

This disclosure further provides, inter alia, human antagonisticanti-human FcRn antibodies that are available for the treatment ofautoimmune disorders and reduction of circulating levels of IgGs. Alsodisclosed is the identification of high affinity soluble Fabs (sFab)with the ability to bind through the antigen binding domain and blockthe interaction between IgG-Fc and human FcRn or rat FcRn (as assessedin both soluble protein and live cell binding assays using a cell lineengineered to overexpress human FcRn or rat FcRn). The sFabs can bindand block in a pH independent fashion or in a pH-dependent fashion,e.g., at an acidic pH such as pH 6. The sFabs can be converted to IgGantibodies.

DEFINITIONS

The term “binding protein” refers to a protein that can interact with atarget molecule. This term is used interchangeably with “ligand.” An“FcRn-binding protein” or “FcRn-binding ligand” refers to a protein thatcan interact with an FcRn, and includes, in particular, proteins thatpreferentially interact with an FcRn, e.g., IgG.

As used herein, the term “antibody” refers to a protein that includes atleast one immunoglobulin variable domain or immunoglobulin variabledomain sequence. For example, an antibody can include a heavy (H) chainvariable region (abbreviated herein as VH), and a light (L) chainvariable region (abbreviated herein as VL). In another example, anantibody includes two heavy (H) chain variable regions and two light (L)chain variable regions. The term “antibody” encompasses antigen-bindingfragments of antibodies (e.g., single chain antibodies, Fab and sFabfragments, F(ab′)₂, Fd fragments, Fv fragments, scFv, and dAb fragments)as well as complete antibodies.

The VH and VL regions can be further subdivided into regions ofhypervariability, termed “complementarity determining regions” (“CDR”),interspersed with regions that are more conserved, termed “frameworkregions” (“FR”). The extent of the framework region and CDR's has beenprecisely defined (see, Kabat, E. A., et al. (1991) Sequences ofProteins of Immunological Interest, Fifth Edition, U.S. Department ofHealth and Human Services, NIH Publication No. 91-3242, and Chothia, C.et al. (1987) J. Mol. Biol. 196:901-917, see alsohttp://www.hgmp.mrc.ac.uk). Kabat definitions are used herein. Each VHand VL is typically composed of three CDR's and four FR's, arranged fromamino-terminus to carboxy-terminus in the following order: FR1, CDR1,FR2, CDR2, FR3, CDR3, FR4.

The term “antigen-binding fragment” of a full length antibody (or simply“antibody portion,” or “fragment”), as used herein, refers to one ormore fragments of a full-length antibody that retain the ability tospecifically bind to a target of interest. Examples of binding fragmentsencompassed within the term “antigen-binding fragment” of a full lengthantibody include (i) a Fab fragment, a monovalent fragment consisting ofthe VL, VH, CL and CH1 domains; (ii) a F(ab′)₂ fragment, a bivalentfragment including two Fab fragments linked by a disulfide bridge at thehinge region; (iii) a Fd fragment consisting of the VH and CH1 domains;(iv) a Fv fragment consisting of the VL and VH domains of a single armof an antibody, (v) a dAb fragment (Ward et al., (1989) Nature341:544-546), which consists of a VH domain; and (vi) an isolatedcomplementarity determining region (CDR) that retains functionality.Furthermore, although the two domains of the Fv fragment, VL and VH, arecoded for by separate genes, they can be joined, using recombinantmethods, by a synthetic linker that enables them to be made as a singleprotein chain in which the VL and VH regions pair to form monovalentmolecules known as single chain Fv (scFv). See e.g., Bird et al. (1988)Science 242:423-426; and Huston et al. (1988) Proc. Natl. Acad. Sci. USA85:5879-5883.

Antibody fragments can be obtained using any appropriate techniqueincluding conventional techniques known to those with skill in the art.The term “monospecific antibody” refers to an antibody that displays asingle binding specificity and affinity for a particular target, e.g.,epitope. This term includes a “monoclonal antibody” or “monoclonalantibody composition,” which as used herein refer to a preparation ofantibodies or fragments thereof of single molecular composition. As usedherein, “isotype” refers to the antibody class (e.g., IgM or IgG1) thatis encoded by heavy chain constant region genes.

As used herein, “binding affinity” refers to the apparent associationconstant or K_(a). The K_(a) is the reciprocal of the dissociationconstant (K_(d)). A binding protein may, for example, have a bindingaffinity of at least 10⁻⁵, 10⁻⁶, 10⁻⁷, 10⁻⁸, 10⁻⁹, 10⁻¹° and 10⁻¹¹ M fora particular target molecule. Higher affinity binding of a bindingligand to a first target relative to a second target can be indicated bya higher K_(a) (or a smaller numerical value K_(d)) for binding thefirst target than the K_(a) (or numerical value K_(a)) for binding thesecond target. In such cases, the binding protein has specificity forthe first target (e.g., a protein in a first conformation or mimicthereof) relative to the second target (e.g., the same protein in asecond conformation or mimic thereof; or a second protein). Differencesin binding affinity (e.g., for specificity or other comparisons) can beat least 1.5, 2, 3, 4, 5, 10, 15, 20, 50, 70, 80, 100, 500, 1000, or 10⁵fold.

Binding affinity can be determined by a variety of methods includingequilibrium dialysis, equilibrium binding, gel filtration, ELISA,surface plasmon resonance, or spectroscopy (e.g., using a fluorescenceassay). Exemplary conditions for evaluating binding affinity are in PBS(phosphate buffered saline) at pH 7.2 at 30° C. These techniques can beused to measure the concentration of bound and free binding protein as afunction of binding protein (or target) concentration. The concentrationof bound binding protein ([Bound]) is related to the concentration offree binding protein ([Free]) and the concentration of binding sites forthe binding protein on the target where (N) is the number of bindingsites per target molecule by the following equation:

[Bound]=N[Free]/((1/Ka)+[Free]).

It is not always necessary to make an exact determination of K_(a),though, since sometimes it is sufficient to obtain a quantitativemeasurement of affinity, e.g., determined using a method such as ELISAor FACS analysis, is proportional to K_(a), and thus can be used forcomparisons, such as determining whether a higher affinity is, e.g.,2-fold higher, to obtain a qualitative measurement of affinity, or toobtain an inference of affinity, e.g., by activity in a functionalassay, e.g., an in vitro or in vivo assay.

The term “cognate ligand” refers to a naturally occurring ligand of anFcRn, including naturally occurring variants thereof (e.g., splicevariants, naturally occurring mutants, and isoforms).

A “conservative amino acid substitution” is one in which the amino acidresidue is replaced with an amino acid residue having a similar sidechain. Families of amino acid residues having similar side chains havebeen defined in the art. These families include amino acids with basicside chains (e.g., lysine, arginine, histidine), acidic side chains(e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g.,glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine),nonpolar side chains (e.g., alanine, valine, leucine, isoleucine,proline, phenylalanine, methionine, tryptophan), beta-branched sidechains (e.g., threonine, valine, isoleucine) and aromatic side chains(e.g., tyrosine, phenylalanine, tryptophan, histidine). It is possiblefor many framework and CDR amino acid residues to include one or moreconservative substitutions.

Consensus sequences for biopolymers can include positions which can bevaried among various amino acids. For example, the symbol “X” in such acontext generally refers to any amino acid (e.g., any of the twentynatural amino acids or any of the nineteen non-cysteine amino acids).Other allowed amino acids can also be indicated for example, usingparentheses and slashes. For example, “(A/W/F/N/Q)” means that alanine,tryptophan, phenylalanine, asparagine, and glutamine are allowed at thatparticular position.

An “effectively human” immunoglobulin variable region is animmunoglobulin variable region that includes a sufficient number ofhuman framework amino acid positions such that the immunoglobulinvariable region does not elicit an immunogenic response in a normalhuman. An “effectively human” antibody is an antibody that includes asufficient number of human amino acid positions such that the antibodydoes not elicit an immunogenic response in a normal human.

An “epitope” refers to the site on a target compound that is bound by abinding protein (e.g., an antibody such as a Fab or full lengthantibody). In the case where the target compound is a protein, the sitecan be entirely composed of amino acid components, entirely composed ofchemical modifications of amino acids of the protein (e.g., glycosylmoieties), or composed of combinations thereof. Overlapping epitopesinclude at least one common amino acid residue.

Calculations of “homology” or “sequence identity” between two sequences(the terms are used interchangeably herein) are performed as follows.The sequences are aligned for optimal comparison purposes (e.g., gapscan be introduced in one or both of a first and a second amino acid ornucleic acid sequence for optimal alignment and non-homologous sequencescan be disregarded for comparison purposes). The optimal alignment isdetermined as the best score using the GAP program in the GCG softwarepackage with a Blosum 62 scoring matrix with a gap penalty of 12, a gapextend penalty of 4, and a frameshift gap penalty of 5. The amino acidresidues or nucleotides at corresponding amino acid positions ornucleotide positions are then compared. When a position in the firstsequence is occupied by the same amino acid residue or nucleotide as thecorresponding position in the second sequence, then the molecules areidentical at that position (as used herein amino acid or nucleic acid“identity” is equivalent to amino acid or nucleic acid “homology”). Thepercent identity between the two sequences is a function of the numberof identical positions shared by the sequences.

In one embodiment, the length of a reference sequence aligned forcomparison purposes is at least 30%, at least 40%, at least 50%, atleast 60%, at least 70%, 80%, 90%, 92%, 95%, 97%, 98%, or 100% of thelength of the reference sequence. For example, the reference sequencemay be the length of the immunoglobulin variable domain sequence.

A “humanized” immunoglobulin variable region is an immunoglobulinvariable region that is modified to include a sufficient number of humanframework amino acid positions such that the immunoglobulin variableregion does not elicit an immunogenic response in a normal human.Descriptions of “humanized” immunoglobulins include, for example, U.S.Pat. No. 6,407,213 and U.S. Pat. No. 5,693,762.

As used herein, the term “hybridizes under low stringency, mediumstringency, high stringency, or very high stringency conditions”describes conditions for hybridization and washing. Guidance forperforming hybridization reactions can be found in Current Protocols inMolecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6, which isincorporated by reference. Aqueous and non-aqueous methods are describedin that reference and either can be used. Specific hybridizationconditions referred to herein are as follows: (1) low stringencyhybridization conditions in 6× sodium chloride/sodium citrate (SSC) atabout 45°., followed by two washes in 0.2×SSC, 0.1% SDS at least at 50°C. (the temperature of the washes can be increased to 55° C. for lowstringency conditions); (2) medium stringency hybridization conditionsin 6×SSC at about 45° C., followed by one or more washes in 0.2° SSC,0.1% SDS at 60° C.; (3) high stringency hybridization conditions in6×SSC at about 45° C., followed by one or more washes in 0.2×SSC, 0.1%SDS at 65° C.; and (4) very high stringency hybridization conditions are0.5M sodium phosphate, 7% SDS at 65° C., followed by one or more washesat 0.2×SSC, 1% SDS at 65° C. Very high stringency conditions (4) are thepreferred conditions and the ones that should be used unless otherwisespecified. The disclosure includes nucleic acids that hybridize withlow, medium, high, or very high stringency to a nucleic acid describedherein or to a complement thereof, e.g., nucleic acids encoding abinding protein described herein. The nucleic acids can be the samelength or within 30, 20, or 10% of the length of the reference nucleicacid. The nucleic acid can correspond to a region encoding animmunoglobulin variable domain sequence.

An FcRn binding protein may have mutations (e.g., at least one, two, orfour, and/or less than 15, 10, 5, or 3) relative to a binding proteindescribed herein (e.g., a conservative or non-essential amino acidsubstitutions), which do not have a substantial effect on the proteinfunctions. Whether or not a particular substitution will be tolerated,i.e., will not adversely affect biological properties, such as bindingactivity can be predicted, e.g., using the method of Bowie, et al.(1990) Science 247:1306-1310.

An “immunoglobulin domain” refers to a domain from the variable orconstant domain of immunoglobulin molecules. Immunoglobulin domainstypically contain two 13-sheets formed of about seven β-strands, and aconserved disulphide bond (see, e.g., A. F. Williams and A. N. Barclay1988 Ann. Rev Immunol. 6:381-405).

As used herein, an “immunoglobulin variable domain sequence” refers toan amino acid sequence which can form the structure of an immunoglobulinvariable domain such that one or more CDR regions are positioned in aconformation suitable for an antigen binding site. For example, thesequence may include all or part of the amino acid sequence of anaturally-occurring variable domain. For example, the sequence may omitone, two or more N- or C-terminal amino acids, internal amino acids, mayinclude one or more insertions or additional terminal amino acids, ormay include other alterations. In one embodiment, a polypeptide thatincludes immunoglobulin variable domain sequence can associate withanother immunoglobulin variable domain sequence to form a target bindingstructure (or “antigen binding site”), e.g., a structure thatpreferentially interacts with an FcRn structure.

The VH or VL chain of the antibody can further include all or part of aheavy or light chain constant region, to thereby form a heavy or lightimmunoglobulin chain, respectively. In one embodiment, the antibody is atetramer of two heavy immunoglobulin chains and two light immunoglobulinchains, wherein the heavy and light immunoglobulin chains areinter-connected by, e.g., disulfide bonds. The heavy chain constantregion includes three domains, CH1, CH2 and CH3. The light chainconstant region includes a CL domain. The variable region of the heavyand light chains contains a binding domain that interacts with anantigen. The constant regions of the antibodies typically mediate thebinding of the antibody to host tissues or factors, including variouscells of the immune system (e.g., effector cells) and the firstcomponent (Clq) of the classical complement system. The term “antibody”includes intact immunoglobulins of types IgA, IgG, IgE, IgD, IgM (aswell as subtypes thereof). The light chains of the immunoglobulin may beof types: kappa or lambda. In one embodiment, the antibody isglycosylated. An antibody can be functional for antibody-dependentcytotoxicity and/or complement-mediated cytotoxicity.

One or more regions of an antibody can be human or effectively human.For example, one or more of the variable regions can be human oreffectively human. For example, one or more of the CDRs can be human,e.g., HC CDR1, HC CDR2, HC CDR3, LC CDR1, LC CDR2, and LC CDR3. Each ofthe light chain CDRs can be human. HC CDR3 can be human. One or more ofthe framework regions can be human, e.g., FR1, FR2, FR3, and FR4 of theHC or LC. In one embodiment, all the framework regions are human, e.g.,derived from a human somatic cell, e.g., a hematopoietic cell thatproduces immunoglobulins or a non-hematopoietic cell. In one embodiment,the human sequences are germline sequences, e.g., encoded by a germlinenucleic acid. One or more of the constant regions can be human oreffectively human. In one embodiment, at least 70, 75, 80, 85, 90, 92,95, or 98% of, or the entire of, the antibody can be human oreffectively human.

All or part of an antibody can be encoded by an immunoglobulin gene or asegment thereof. Exemplary human immunoglobulin genes include the kappa,lambda, alpha (IgA1 and IgA2), gamma (IgG1, IgG2, IgG3, IgG4), delta,epsilon and mu constant region genes, as well as the myriadimmunoglobulin variable region genes. Full-length immunoglobulin “lightchains” (about 25 KDa or 214 amino acids) are encoded by a variableregion gene at the NH2-terminus (about 110 amino acids) and a kappa orlambda constant region gene at the COOH-terminus. Full-lengthimmunoglobulin “heavy chains” (about 50 KDa or 446 amino acids), aresimilarly encoded by a variable region gene (about 116 amino acids) andone of the other aforementioned constant region genes, e.g., gamma(encoding about 330 amino acids).

An “isolated composition” refers to a composition that is removed fromat least 90% of at least one component of a natural sample from whichthe isolated composition can be obtained. Compositions producedartificially or naturally can be “compositions of at least” a certaindegree of purity if the species or population of species of interests isat least 5, 10, 25, 50, 75, 80, 90, 92, 95, 98, or 99% pure on aweight-weight basis.

The term “mimic,” in the context of a mimic of a conformation of an FcRnor portion thereof, refers to a modified FcRn which has a bias for atleast one particular conformation relative to a naturally occurringFcRn, or portion thereof.

A “non-essential” amino acid residue is a residue that can be alteredfrom the wild-type sequence of the binding agent, e.g., the antibody,without abolishing or without substantially altering a biologicalactivity, whereas an “essential” amino acid residue results in such achange.

The phrases “parenteral administration” and “administered parenterally”as used herein means modes of administration other than enteral andtopical administration, usually by injection, and includes, withoutlimitation, intravenous, intramuscular, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular,subarachnoid, intraspinal, epidural and intrasternal injection andinfusion.

The terms “polypeptide” or “peptide” (which may be used interchangeably)refer to a polymer of three or more amino acids linked by a peptidebond, e.g., between 3 and 30, 12 and 60, or 30 and 300, or over 300amino acids in length. The polypeptide may include one or more unnaturalamino acids. Typically, the polypeptide includes only natural aminoacids. A “protein” can include one or more polypeptide chains.Accordingly, the term “protein” encompasses polypeptides. A protein orpolypeptide can also include one or more modifications, e.g., aglycosylation, amidation, phosphorylation, nitrosylation, and so forth.The term “small peptide” can be used to describe a polypeptide that isbetween 3 and 30 amino acids in length, e.g., between 8 and 24 aminoacids in length.

A “prophylactically effective amount” refers to an amount effective, atdosages and for periods of time necessary, to achieve the desiredprophylactic result. Typically, because a prophylactic dose is used insubjects prior to or at an earlier stage of disease, theprophylactically effective amount will be less than the therapeuticallyeffective amount.

As used herein, the term “substantially identical” (or “substantiallyhomologous”) is used herein to refer to a first amino acid or nucleicacid sequence that contains a sufficient number of identical orequivalent (e.g., with a similar side chain, e.g., conserved amino acidsubstitutions) amino acid residues or nucleotides to a second amino acidor nucleic acid sequence such that the first and second amino acid ornucleic acid sequences have (or encode proteins having) similaractivities, e.g., a binding activity, a binding preference, or abiological activity. In the case of antibodies, the second antibody hasthe same specificity and has at least 50% of the affinity relative tothe same antigen.

Sequences similar or homologous (e.g., at least about 85% sequenceidentity) to the sequences disclosed herein are also part of thisapplication. In some embodiments, the sequence identity can be about85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or higher. Inaddition, substantial identity exists when the nucleic acid segmentshybridize under selective hybridization conditions (e.g., highlystringent hybridization conditions), to the complement of the strand.The nucleic acids may be present in whole cells, in a cell lysate, or ina partially purified or substantially pure form.

Statistical significance can be determined by any art known method.Exemplary statistical tests include: the Students T-test, Mann Whitney Unon-parametric test, and Wilcoxon non-parametric statistical test. Somestatistically significant relationships have a P value of less than 0.05or 0.02. Particular binding proteins may show a difference, e.g., inspecificity or binding, that are statistically significant (e.g., Pvalue<0.05 or 0.02). The terms “induce”, “inhibit”, “potentiate”,“elevate”, “increase”, “decrease” or the like, e.g., which denotedistinguishable qualitative or quantitative differences between twostates, and may refer to a difference, e.g., a statistically significantdifference, between the two states.

A “therapeutically effective dosage” modulates a measurable parameter,e.g., levels of circulating IgG antibodies by a statisticallysignificant degree or at least about 20%, by at least about 40%, by atleast about 60%, or by at least about 80% relative to untreatedsubjects. The ability of a compound to modulate a measurable parameter,e.g., autoimmunity, can be evaluated in an animal model systempredictive of efficacy in human autoimmune disorders. Alternatively,this property of a composition can be evaluated by examining the abilityof the compound to modulate a parameter in vitro, e.g., by assays knownto the skilled practitioner.

Other features and advantages of the instant invention will become moreapparent from the following detailed description and claims. Embodimentsof the invention can include any combination of features describedherein. In no case does the term “embodiment” exclude one or more otherfeatures disclosed herein.

FcRn Sequences

The following sequence alignment is of a human FcRn alpha chain aminoacid sequence with a rat FcRn alpha chain amino acid sequence Anexemplary FcRn protein can include one of these two sequences, or afragment thereof, e.g., a fragment without the signal sequence:

  Signal Sequence                     α₁ domain α_HUMAN:MGVPPPQPWALGLLLFLLPGGLG AESHLSLLYHLTAVSSPAPGTPAFWVSGWLGPQQYLS α_RAT:MGMSQPGV-LLSLLLVLLPQTWG AEPRLPLMYHLAAVSDLSTGLPSFWATGWLGAQQYLT                    α₁ domain                        α₂ domain α_HUMAN:YNSLRGEAEPCGAWVWENQVSWYWEKETTDLRIKEKLFLEAFKALGGK--GP YTLQGLLG α_RAT:YNNLRQEADPCGAWIWENQVSWYWEKETTDLKSKEQLFLEAIRTLENQINGT FTLQGLLG                    α₂ domain α_HUMAN:CELGPDNTSVPTAKFALNGEEFMNFDLKQGTWGGDWPEALAISQRWQQQDKAANKELTFL □_RAT:CELAPDNSSLPTAVFALNGEEFMRFNPRTGNWSGEWPETDIVGNLWMKQPEAARKESEFL  α₂ domain                           α₃ domain α_HUMAN:LFSCPHRLREHLERGRGNLEWK EPPSMRLKARPSSPGFSVLTCSAFSFYPPELQLRFLRN α_RAT:LTSCPERLLGHLERGRQNLEWK EPPSMRLKARPGNSGSSVLTCAAFSFYPPELKFRFLRN                    α₃ domain □_HUMAN:GLAAGTGQGDFGPNSDGSFHASSSLTVKSGDEHHYCCIVQHAGLAQPLRVELE □_RAT:GLASGSGNCSTGPNGDGSFHAWSLLEVKRGDEHHYQCQVEHEGLAQPLTVDLD           Transmembrane              Cytoplasmic domain α_HUMAN:SPAKSSVLVVGIVIGVLLLTAAAVGGALLW RRMRSGLPAPWISLRGDDTGVLLPTPGEAQ α_RAT:SPARSSVPVVGIILGLLLVVVAIAGGVLLW NRMRSGLPAPWLSLSGDDSGDLLPGGNLPP α_HUMAN:DADLKDVNVIPATA (SEQ ID NO: 1) α_RAT: EAEPQGVNAFPATS (SEQ ID NO: 2)

The following sequence alignment is of a human β2 microglobulin aminoacid sequence with a rat β₂ microglobulin amino acid sequence. Anexemplary FcRn protein can include one of these two sequences, or afragment thereof, e.g., a fragment without the signal sequence:

 Signal Sequence               β2 microglobulin β2m_human:MSRSVALAVLALLSLSGLEA IQRTPKIQVYSRHPAENGKSNFLNCYVSGFHPSDIEVDLL β2m_rat:MARSVTVIFLVLVSLAVVLA IQKTPQIQVYSRHPPENGKPNFLNCYVSQFHPPQIEIELL                   β2 microglobulin β2m_human:KNGERIEKVEHSDLSFSKDWSFYLLYYTEFTPTEKDEYACRVNHVTLSQPKIVKWDRDM (SEQ ID NO: 3)β2m_rat:KNGKKIPNIEMSDLSFSKDWSFYILAHTEFTPTETDVYACRVKHVTLKEPKTVTWDRDM (SEQ ID NO: 4)An exemplary nucleic acid sequence encoding an FcRn protein alpha chaincan include the following sequences:

FcRN alpha nucleotide sequence Homo sapiens (SEQ ID NO: 5)GTTCTTCAGGTACGAGGAGGGCATTGTTGTCAGTCTGGACCGAGCCCGCAGAGCCCCTCCTCGGCGTCCTGGTCCCGGCCGTGCCCGCGGTGTCCCGGGAGGAAGGGGCGGGCCGGGGGTCGGGAGGAGTCACGTGCCCCCTCCCGCCCCAGGTCGTCCTCTCAGCATGGGGGTCCCGCGGCCTCAGCCCTGGGCGCTGGGGCTCCTGCTCTTTCTCCTTCCTGGGAGCCTGGGCGCAGAAAGCCACCTCTCCCTCCTGTACCACCTTACCGCGGTGTCCTCGCCTGCCCCGGGGACTCCTGCCTTCTGGGTGTCCGGCTGGCTGGGCCCGCAGCAGTACCTGAGCTACAATAGCCTGCGGGGCGAGGCGGAGCCCTGTGGAGCTTGGGTCTGGGAAAACCAGGTGTCCTGGTATTGGGAGAAAGAGACCACAGATCTGAGGATCAAGGAGAAGCTCTTTCTGGAAGCTTTCAAAGCTTTGGGGGGAAAAGGTCCCTACACTCTGCAGGGCCTGCTGGGCTGTGAACTGGGCCCTGACAACACCTCGGTGCCCACCGCCAAGTTCGCCCTGAACGGCGAGGAGTTCATGAATTTCGACCTCAAGCAGGGCACCTGGGGTGGGGACTGGCCCGAGGCCCTGGCTATCAGTCAGCGGTGGCAGCAGCAGGACAAGGCGGCCAACAAGGAGCTCACCTTCCTGCTATTCTCCTGCCCGCACCGCCTGCGGGAGCACCTGGAGAGGGGCCGCGGAAACCTGGAGTGGAAGGAGCCCCCCTCCATGCGCCTGAAGGCCCGACCCAGCAGCCCTGGCTTTTCCGTGCTTACCTGCAGCGCCTTCTCCTTCTACCCTCCGGAGCTGCAACTTCGGTTCCTGCGGAATGGGCTGGCCGCTGGCACCGGCCAGGGTGACTTCGGCCCCAACAGTGACGGATCCTTCCACGCCTCGTCGTCACTAACAGTCAAAAGTGGCGATGAGCACCACTACTGCTGCATTGTGCAGCACGCGGGGCTGGCGCAGCCCCTCAGGGTGGAGCTGGAATCTCCAGCCAAGTCCTCCGTGCTCGTGGTGGGAATCGTCATCGGTGTCTTGCTACTCACGGCAGCGGCTGTAGGAGGAGCTCTGTTGTGGAGAAGGATGAGGAGTGGGCTGCCAGCCCCTTGGATCTCCCTTCGTGGAGACGACACCGGGGTCCTCCTGCCCACCCCAGGGGAGGCCCAGGATGCTGATTTGAAGGATGTAAATGTGATTCCAGCCACCGCCTGACCATCCGCCATTCCGACTGCTAAAAGCGAATGTAGTCAGGCCCCTTTCATGCTGTGAGACCTCCTGGAACACTGGCATCTCTGAGCCTCCAGAAGGGGTTCTGGGCCTAGTTGTCCTCCCTCTGGAGCCCCGTCCTGTGGTCTGCCTCAGTTTCCCCTCCTAATACATATGGCTGTTTTCCACCTCGATAATATAACACGAGTTTGGGCCCGAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAA

The nucleic acid sequence of an exemplary human FeRn (extra-cellulardomain) plus GPI DNA sequences (lowercase bold) is set forth below.

(SEQ ID NO: 6) ATGGGGGTCCCGCGGCCTCAGCCCTGGGCGCTGGGGCTCCTGCTCTTTCTCCTTCCTGGGAGCCTGGGCGCAGAAAGCCACCTCTCCCTCCTGTACCACCTTACCGCGGTGTCCTCGCCTGCCCCGGGGACTCCTGCCTTCTGGGTGTCCGGCTGGCTGGGCCCGCAGCAGTACCTGAGCTACAATAGCCTGCGGGGCGAGGCGGAGCCCTGTGGAGCTTGGGTCTGGGAAAACCAGGTGTCCTGGTATTGGGAGAAAGAGACCACAGATCTGAGGATCAAGGAGAAGCTCTTTCTGGAAGCTTTCAAAGCTTTGGGGGGAAAAGGTCCCTACACTCTGCAGGGCCTGCTGGGCTGTGAACTGGGCCCTGACAACACCTCGGTGCCCACCGCCAAGTTCGCCCTGAACGGCGAGGAGTTCATGAATTTCGACCTCAAGCAGGGCACCTGGGGTGGGGACTGGCCCGAGGCCCTGGCTATCAGTCAGCGGTGGCAGCAGCAGGACAAGGCGGCCAACAAGGAGCTCACCTTCCTGCTATTCTCCTGCCCGCACCGCCTGCGGGAGCACCTGGAGAGGGGCCGCGGAAACCTGGAGTGGAAGGAGCCCCCCTCCATGCGCCTGAAGGCCCGACCCAGCAGCCCTGGCTTTTCCGTGCTTACCTGCAGCGCCTTCTCCTTCTACCCTCCGGAGCTGCAACTTCGGTTCCTGCGGAATGGGCTGGCCGCTGGCACCGGCCAGGGTGACTTCGGCCCCAACAGTGACGGATCCTTCCACGCCTCGTCGTCACTAACAGTCAAAAGTGGCGATGAGCACCACTACTGCTGCATTGTGCAGCACGCGGGGCTGGCGCAGCCCCTCAGGGTGGAGCTGGAATCTCCAGCCAAGTCCTCCcggccgctcgacgggctacgagcatcagtaacactactaggcgcaggcctactactatcactactaccagcactactacgatttgggccataa

An exemplary nucleic acid sequence encoding a Beta-2-microglobulin (β2M)can include the following sequences:

> Beta-2-microglobulin (β2M) nucleotide Homo sapiens (SEQ ID NO: 7)AATATAAGTGGAGGCGTCGCGCTGGCGGGCATTCCTGAAGCTGACAGCATTCGGGCCGAGATGTCTCGCTCCGTGGCCTTAGCTGTGCTCGCGCTACTCTCTCTTTCTGGCCTGGAGGCTATCCAGCGTACTCCAAAGATTCAGGTTTACTCACGTCATCCAGCAGAGAATGGAAAGTCAAATTTCCTGAATTGCTATGTGTCTGGGTTTCATCCATCCGACATTGAAGTTGACTTACTGAAGAATGGAGAGAGAATTGAAAAAGTGGAGCATTCAGACTTGTCTTTCAGCAAGGACTGGTCTTTCTATCTCTTGTACTACACTGAATTCACCCCCACTGAAAAAGATGAGTATGCCTGCCGTGTGAACCATGTGACTTTGTCACAGCCCAAGATAGTTAAGTGGGATCGAGACATGTAAGCAGCATCATGGAGGTTTGAAGATGCCGCATTTGGATTGGATGAATTCCAAATTCTGCTTGCTTGCTTTTTAATATTGATATGCTTATACACTTACACTTTATGCACAAAATGTAGGGTTATAATAATGTTAACATGGACATGATCTTCTTTATAATTCTACTTTGAGTGCTGTCTCCATGTTTGATGTATCTGAGCAGGTTGCTCCACAGGTAGCTCTAGGAGGGCTGGCAACTTAGAGGTGGGGAGCAGAGAATTCTCTTATCCAACATCAACATCTTGGTCAGATTTGAACTCTTCAATCTCTTGCACTCAAAGCTTGTTAAGATAGTTAAGCGTGCATAAGTTAACTTCCAATTTACATACTCTGCTTAGAATTTGGGGGAAAATTTAGAAATATAATTGACAGGATTATTGGAAATTTGTTATAATGAATGAAACATTTTGTCATATAAGATTCATATTTACTTCTTATACATTTGATAAAGTAAGGCATGGTTGTGGTTAATCTGGTTTATTTTTGTTCCACAAGTTAAATAAATCATAAAACTTGATGTGTTATCTCTTA

Mouse Anti-Human FcRn Antibodies Antibody Structure and Sequences

The invention relates to an antibody that specifically binds at leastone FcRn epitope, wherein binding of the antibody to the FcRn epitopeinhibits the Fc portion of IgG from binding to the FcRn. The inventionthus relates to a FcRn blocking antibody. The blocking antibody can bean IgG, an IgM, an IgA, an IgD or an IgE. In one embodiment the blockingantibody is an IgG. In one embodiment the antibody of the invention willhave a binding affinity of 10¹⁰ M⁻¹. In another embodiment the antibodyof the invention will have a binding affinity of 10¹¹M⁻¹.

In one embodiment the invention relates to a monoclonal antibodyproduced by a 3B3.11 hybridoma, a 31.1 hybridoma, a 4B4.12 hybridoma, ora 17D3 hybridoma.

In one embodiment the invention relates to an antibody which binds to anFcRn linear epitope. In another embodiment the invention relates to anantibody which binds to an FcRn conformational epitope. In oneembodiment the antibody of the invention binds to an amino acid sequencecomprising EPPSMRLKAR (SEQ ID NO: 105) or a fragment thereof. In anotherembodiment the antibody of the invention binds to an amino acid sequencecomprising CSAFYPPELQLRFFLRNGL (SEQ ID NO:106) or a fragment thereof.

In certain embodiments, antibodies of this invention specifically reactwith an epitope that is the same as the epitope recognized by 3B3.11 and31.1. Such antibodies can be determined in competitive binding assays.

Amino acid (AA) sequences of illustrative embodiments of the anti-FcRnantibodies of this invention, including their V_(H) and V_(L) domains,and CDRs, are enumerated in Table 1. Two specific embodiments of theantibodies are identified as 3B3.11 and 31.1.

TABLE 1 CDR's For Mouse Antibodies Of The Invention. HV- AntibodyLV-CDR1 LV-CDR2 LV-CDR3 CDR1 HV-CDR2 HV-CDR3 3B3.11 SASSSISSNYLH RTSNLASQQGSNIPLT RSWMN RIHPGDGDTNYN EGSPYFDY (SEQ ID NO: 8) (SEQ ID (SEQ ID(SEQ ID GKFKG (SEQ ID (SEQ ID NO: 9) NO: 10) NO: 11) NO: 12) NO: 13)31.1 KASQDINNYIA YTSTLQP LQYDNLLRT DYAMH VITNYYGDASYN GGYDGYY(SEQ ID NO: 14) (SEQ ID (SEQ ID (SEQ ID QKFKG (SEQ ID VDFDY NO: 15)NO: 16) NO: 17) NO: 18) (SEQ ID NO: 19)

The amino acid sequence for the 3B3.11 light chain is set forth below.The CDR regions are underlined and the constant region is in italics.

(SEQ ID NO: 20)                            CDR 1                       CDR 2 1DIQLTQSPTT VAASPGEKIT ITC SASSSIS SNYLH WYQQK PGFSPKLLIY  RTSNLAS GVP                                 CDR 3                    CL 1 61ARFSGSGSGT SYSLTIGTME AEDVATYYC Q QGSNIPLT FG AGTKLELKRA DAAPTVSIFP                            CL 1 121PSSEQLTSGG ASVVCFLNNF YPKDINVKWK IDGSERQNGV LNSWTDQDSK DSTYSMSSTL               CL 1 181 TLTKDEYERH NSYTCEATHK TSTSPIVKSF NKNE

The amino acid sequence for the 3B3.11 heavy chain is set forth below.The CDR regions are underlined and the constant region is in italics.

(SEQ ID NO: 21)                                CDR 1                   CDR 2 1VKLQESGPEL VKPGASVKIS CKASGYAFS R SWMN WVKQRP GQGLEWIG RI HPGDGDTNYNCDR 2                                    CDR 3               CH 1 61GKFKG KATLT VAKSSSTAYM QLSSLTSVDS AVYFCAN EGS PYFDY WGQGT TLTVSSAKTT                            CH 1 121PPSVYPLAPG SAAQTNSMVT LGCLVKGYFP EPVTVTWNSG SLSSGVHTFP AVLQSDLYTL               CH 1 181 SSSVTVPSST WPSETVTCNV AHPASSTKVD KKLE

The amino acid sequence for the 31.1 light chain is set forth below. TheCDR regions are underlined and the constant region is in italics.

(SEQ ID NO: 22)                             CDR 1                    CDR 2 1DIQLTQSPSS LSASLGDKVT ITC KASQDIN NYIA WYQHKP GKRSRLLIH Y TSTLQP GIPS                                CDR 3                   CL 1 61RFSGSGSGRD YSFSISNLEP EDIATYYC LQ YDNLLRT FGG GTKLEIKRAD AAPTVSIFPP                            CL 1 121SSEQLTSGGA SVVCFLNNFY PKDINVKWKI DGSERQNGVL NSWTDQDSKD STYSMSSTLT              CL 1 181 LTKDEYERHN SYTCEATHKT STSPIVKSFN KNE

The amino acid sequence for the 31.1 heavy chain is set forth below. TheCDR regions are underlined and the constant region is in italics.

(SEQ ID NO: 23)                               CDR 1                   CDR 2 1VXLQQSGAEL VRPGVSVKIS CKGSGYTFT D YAMH WVKQSH AKSLEWIG VI TNYYGDASYNCDR 2                                      CDR 3 61 QKFKGKATMT VDKSSSTAYM ELARLTSEDS AIYYCAR GGY DGYYVDFDY W GQGTTLTVSS                            CL 1 121AKTTPPSVYP LAPGSAAQTN SMVTLGCLVK GYFPEPVTVT WNSGSLSSGV HTFPAVLQSD                 CL 1 181 LYTLSSSVTV PSSTWPSETV TCNVAHPASS TKVDKKLE

Certain embodiments comprise a VH domain, a VL domain, or a combinationthereof, of the Fv fragment from 3B3.11 and 31.1. Further embodimentscomprise one, two, three, four, five or six complementarity determiningregions (CDRs) from the VH and VL domains. Antibodies whose CDRsequences are included within SEQ ID NO: 20, 21, 22, or 23 areencompassed within the scope of this invention.

The disclosure provides a method for obtaining anti-FcRn antibodies thatcomprise creating antibodies with altered VH and/or VL sequence(s)obtained from SEQ ID NOS: 20, 21, 22, or 23. Such antibodies may bederived by a skilled artisan using techniques known in the art. Forexample, amino acid substitutions, deletions, or additions can beintroduced in FR and/or CDR regions. FR changes are usually designed toimprove the stability and immunogenicity of the antibody, while CDRchanges are typically designed to increase antibody affinity for itsantigen. The changes that increase affinity may be tested by alteringCDR sequence and measuring antibody affinity for its target (AntibodyEngineering, 2nd ed., Oxford University Press, ed. Borrebaeck (1995).

Antibodies whose CDR sequences differ insubstantially from thoseincluded in or included within the sequences in SEQ ID NOS: 20, 21, 22,or 23 are encompassed within the scope of this invention. Typically,this involves substitution of an amino acid with an amino acid havingsimilar charge, hydrophobic, or stereochemical characteristics. Moredrastic substitutions in FR regions, in contrast to CDR regions, mayalso be made as long as they do not adversely affect (e.g., reduceaffinity by more than 50% as compared to unsubstituted antibody) thebinding properties of the antibody. Substitutions may also be made togermline the antibody or stabilize the antigen binding site.

Methods of Making Mouse Monoclonal Antibodies

Methods of making monoclonal antibodies have been described (Harlow etal., Antibodies A Laboratory Manual, Cold Spring Harbor Laboratory, ColdSpring Harbor, N.Y. (1988)). In some instances, as a first step, arodent, e.g., a mouse is immunized with an antigenic polypeptide togenerate an antibody response. Because FcRn is expressed ubiquitouslyand exhibits high degree of homology between species, polypeptideimmunization has not been successful in producing high affinity FcRnspecific monoclonal antibodies or FcRn monoclonal blocking antibodies.To solve this problem DNA vaccination can be performed (Castagliola etal., J. Immunology 160:1458 (1998)). DNA vaccination involves immunizinga rodent, e.g., a mouse with a cDNA construct encoding FcRn or afragment thereof. Immunization can be administered intramuscularly,intraperitoneally, subcutaneously, intravenously, intradermally ordirectly into the lymph node. In one embodiment the immunizationsadministered intramuscularly. DNA vaccination can be administered withan adjuvant, e.g. Freunds complete adjuvant or Freund's incompleteadjuvant. The DNA vaccination can be accompanied by administration of acardiotoxin to increase the antibody titer. Administration of acardiotoxin causes cell death and cell regeneration which enhancescellular uptake of the administered DNA vaccine. The cardiotoxin canalso increase inflammation which results in a more robust immuneresponse.

Antibody secreting cells (B cells) are isolated from the rodent.Typically the B cell can be isolated from the rodents spleen and fusedwith a myeloma cell line. The myeloma cell lines are immortalized celllines that do not produce antibodies. The myeloma cell line can bechosen from, but is not limited to P3-X63Ag8, X63Ag8.653, Sp2/0-Ag14,FO, NSI/1-Ag-4-1, NSW, FOX-NY, Y3-Ag1.2.3, YB2/0 and IR983F.

Splenocytes are fused with the myeloma cell line to form a hybridoma.Fusion can be mediated by mixing the two cell types with polyethyleneglycol for an appropriate period of time (e.g. five minutes). The formedhybridomas are grown in cell culture using an appropriate selectionmedia (e.g. HAT) and screened for their ability to produce a monoclonalantibody against FcRn. Screening can be performed using knownimmunological techniques, e.g. an ELISA.

Another approach to making FcRn specific monoclonal antibodies is toimmunize a transgenic FcRn knockout mouse with soluble human FcRn, see,PCT Application WO 02/43658. WO 02/43658 describes a transgenic mousewhose genome comprises a homozygous disruption in its endogenous FcRngene, wherein said homozygous disruption prevents expression of afunctional FcRn protein. The monoclonal antibody of the invention is notmade in a transgenic mouse whose genome comprises a homozygousdisruption in its endogenous FcRn gene, wherein said homozygousdisruption prevents expression of a functional FcRn protein. Themonoclonal antibody of the invention is not comprised of a B cell from atransgenic mouse whose genome comprises a homozygous disruption in itsendogenous FcRn gene, wherein said homozygous disruption preventsexpression of a functional FcRn protein.

Humanized Anti-FcRn Antibodies Display Libraries

A display library can be used to identify antibodies that bind to theFcRn. A display library is a collection of entities; each entityincludes an accessible polypeptide component and a recoverable componentthat encodes or identifies the polypeptide component. The polypeptidecomponent is varied so that different amino acid sequences arerepresented. The polypeptide component can be of any length, e.g. fromthree amino acids to over 300 amino acids. In a selection, thepolypeptide component of each member of the library is probed with theFcRn and if the polypeptide component binds to the FcRn, the displaylibrary member is identified, typically by retention on a support. Inaddition, a display library entity can include more than one polypeptidecomponent, for example, the two polypeptide chains of an sFab.

Retained display library members are recovered from the support andanalyzed. The analysis can include amplification and a subsequentselection under similar or dissimilar conditions. For example, positiveand negative selections can be alternated. The analysis can also includedetermining the amino acid sequence of the polypeptide component andpurification of the polypeptide component for detailed characterization.

A variety of formats can be used for display libraries. Examples includethe following.

Phage Display.

One format utilizes viruses, particularly bacteriophages. This format istermed “phage display.” The protein component is typically covalentlylinked to a bacteriophage coat protein. The linkage results fromtranslation of a nucleic acid encoding the protein component fused tothe coat protein. The linkage can include a flexible peptide linker, aprotease site, or an amino acid incorporated as a result of suppressionof a stop codon. Phage display is described, for example, in U.S. Pat.No. 5,223,409; Smith (1985) Science 228:1315-1317; WO 92/18619; WO91/17271; WO 92/20791; WO 92/15679; WO 93/01288; WO 92/01047; WO92/09690; WO 90/02809; de Haard et al. (1999) J. Biol. Chem.274:18218-30; Hoogenboom et al. (1998) Immunotechnology 4:1-20;Hoogenboom et al. (2000) Immunol Today 2:371-8; Fuchs et al. (1991)Bio/Technology 9:1370-1372; Hay et al. (1992) Hum Antibod Hybridomas3:81-85; Huse et al. (1989) Science 246:1275-1281; Griffiths et al.(1993) EMBO J. 12:725-734; Hawkins et al. (1992) J Mol Biol 226:889-896;Clackson et al. (1991) Nature 352:624-628; Gram et al. (1992) PNAS89:3576-3580; Garrard et al. (1991) Bio/Technology 9:1373-1377; andHoogenboom et al. (1991) Nuc Acid Res 19:4133-4137.

Phage display systems have been developed for filamentous phage (phagefl, fd, and M13) as well as other bacteriophage. The filamentous phagedisplay systems typically use fusions to a minor coat protein, such asgene III protein, and gene VIII protein, a major coat protein, butfusions to other coat proteins such as gene VI protein, gene VIIprotein, gene IX protein, or domains thereof can also been used (see,e.g., WO 00/71694). In one embodiment, the fusion is to a domain of thegene III protein, e.g., the anchor domain or “stump,” (see, e.g., U.S.Pat. No. 5,658,727 for a description of the gene III protein anchordomain). It is also possible to physically associate the protein beingdisplayed to the coat using a non-peptide linkage.

Bacteriophage displaying the protein component can be grown andharvested using standard phage preparatory methods, e.g., PEGprecipitation from growth media. After selection of individual displayphages, the nucleic acid encoding the selected protein components can beisolated from cells infected with the selected phages or from the phagethemselves, after amplification. Individual colonies or plaques can bepicked, the nucleic acid isolated and sequenced.

Other Display Formats.

Other display formats include cell based display (see, e.g., WO03/029456), protein-nucleic acid fusions (see, e.g., U.S. Pat. No.6,207,446), and ribosome display (See, e.g., Mattheakis et al. (1994)Proc. Natl. Acad. Sci. USA 91:9022 and Hanes et al. (2000) NatBiotechnol. 18:1287-92; Hanes et al. (2000) Methods Enzymol. 328:404-30;and Schaffitzel et al. (1999) J Immunol Methods. 231(1-2):119-35).

Scaffolds.

Scaffolds for display can include: antibodies (e.g., Fab fragments,single chain Fv molecules (scFV), single domain antibodies, camelidantibodies, and camelized antibodies); T-cell receptors; MHC proteins;extracellular domains (e.g., fibronectin Type III repeats, EGF repeats);protease inhibitors (e.g., Kunitz domains, ecotin, BPTI, and so forth);TPR repeats; trifoil structures; zinc finger domains; DNA-bindingproteins; particularly monomeric DNA binding proteins; RNA bindingproteins; enzymes, e.g., proteases (particularly inactivated proteases),RNase; chaperones, e.g., thioredoxin and heat shock proteins;intracellular signaling domains (such as SH2 and SH3 domains); linearand constrained peptides; and linear peptide substrates. Displaylibraries can include synthetic and/or natural diversity. See, e.g., US2004-0005709.

Display technology can also be used to obtain antibodies that bindparticular epitopes of a target. This can be done, for example, by usingcompeting non-target molecules that lack the particular epitope or aremutated within the epitope, e.g., with alanine. Such non-targetmolecules can be used in a negative selection procedure as describedbelow, as competing molecules when binding a display library to thetarget, or as a pre-elution agent, e.g., to capture in a wash solutiondissociating display library members that are not specific to thetarget.

Iterative Selection.

In one embodiment, display library technology is used in an iterativemode. A first display library is used to identify one or more antibodiesthat bind a target. These identified antibodies are then varied using amutagenesis method to form a second display library. Higher affinityantibodies are then selected from the second library, e.g., by usinghigher stringency or more competitive binding and washing conditions.

In some implementations, the mutagenesis is targeted to regions known orlikely to be at the binding interface. In the case of antibodies, themutagenesis can be directed to the CDR regions of the heavy or lightchains as described herein. Further, mutagenesis can be directed toframework regions near or adjacent to the CDRs. In the case ofantibodies, mutagenesis can also be limited to one or a few of the CDRs,e.g., to make precise step-wise improvements. Exemplary mutagenesistechniques include: error-prone PCR, recombination, DNA shuffling,site-directed mutagenesis and cassette mutagenesis.

In one example of iterative selection, the methods described herein areused to first identify an antibody from a display library that binds anFcRn with at least a minimal binding specificity for a target or aminimal activity, e.g., an equilibrium dissociation constant for bindingof less than 1 nM, 10 nM, or 100 nM. The nucleic acid sequence encodingthe initial identified antibodies are used as a template nucleic acidfor the introduction of variations, e.g., to identify a second antibodythat has enhanced properties (e.g., binding affinity, kinetics, orstability) relative to the initial antibody.

Off-Rate Selection.

Since a slow dissociation rate can be predictive of high affinity,particularly with respect to interactions between antibodies and theirtargets, the methods described herein can be used to isolate antibodieswith a desired kinetic dissociation rate (e.g., reduced) for a bindinginteraction to a target.

To select for slow dissociating antibodies from a display library, thelibrary is contacted to an immobilized target. The immobilized target isthen washed with a first solution that removes non-specifically orweakly bound biomolecules. Then the bound antibodies are eluted with asecond solution that includes a saturating amount of free target or atarget specific high-affinity competing monoclonal antibody, i.e.,replicates of the target that are not attached to the particle. The freetarget binds to biomolecules that dissociate from the target. Rebindingis effectively prevented by the saturating amount of free targetrelative to the much lower concentration of immobilized target.

The second solution can have solution conditions that are substantiallyphysiological or that are stringent. Typically, the solution conditionsof the second solution are identical to the solution conditions of thefirst solution. Fractions of the second solution are collected intemporal order to distinguish early from late fractions. Later fractionsinclude biomolecules that dissociate at a slower rate from the targetthan biomolecules in the early fractions.

Further, it is also possible to recover display library members thatremain bound to the target even after extended incubation. These caneither be dissociated using chaotropic conditions or can be amplifiedwhile attached to the target. For example, phage bound to the target canbe contacted to bacterial cells.

Selecting or Screening for Specificity.

The display library screening methods described herein can include aselection or screening process that discards display library membersthat bind to a non-target molecule. Examples of non-target moleculesinclude streptavidin on magnetic beads, blocking agents such as bovineserum albumin, non-fat bovine milk, any capturing or target immobilizingmonoclonal antibody, or non-transfected cells which do not express thehuman FcRn target.

In one implementation, a so-called “negative selection” step is used todiscriminate between the target and related non-target molecule and arelated, but distinct non-target molecules. The display library or apool thereof is contacted to the non-target molecule. Members of thesample that do not bind the non-target are collected and used insubsequent selections for binding to the target molecule or even forsubsequent negative selections. The negative selection step can be priorto or after selecting library members that bind to the target molecule.

In another implementation, a screening step is used. After displaylibrary members are isolated for binding to the target molecule, eachisolated library member is tested for its ability to bind to anon-target molecule (e.g., a non-target listed above). For example, ahigh-throughput ELISA screen can be used to obtain this data. The ELISAscreen can also be used to obtain quantitative data for binding of eachlibrary member to the target as well as for cross species reactivity torelated targets or subunits of the target (e.g., rat FcRn; (32microglobulin) and also under different condition such as pH6 or pH 7.5.The non-target and target binding data are compared (e.g., using acomputer and software) to identify library members that specificallybind to the target.

Other Expression Libraries

Other types of collections of proteins (e.g., expression libraries) canbe used to identify proteins with a particular property (e.g., abilityto bind FcRn and/or ability to modulate FcRn), including, e.g., proteinarrays of antibodies (see, e.g., De Wildt et al. (2000) Nat. Biotechnol.18:989-994), lambda gt11 libraries, two-hybrid libraries and so forth.

Antibody Libraries

In one embodiment, the library presents a diverse pool of polypeptides,each of which includes an immunoglobulin domain, e.g., an immunoglobulinvariable domain. Display libraries are particularly useful, for example,for identifying human or “humanized” antibodies that recognize humanantigens. Such antibodies can be used as therapeutics to treat humandisorders such as autoimmune disorders. Because the constant andframework regions of the antibody are human, these therapeuticantibodies may avoid themselves being recognized and targeted asantigens. The constant regions may also be optimized to recruit effectorfunctions of the human immune system. The in vitro display selectionprocess surmounts the inability of a normal human immune system togenerate antibodies against self-antigens.

A typical antibody display library displays a polypeptide that includesa VH domain and a VL domain. An “immunoglobulin domain” refers to adomain from the variable or constant domain of immunoglobulin molecules.Immunoglobulin domains typically contain two β-sheets formed of aboutseven β-strands, and a conserved disulphide bond (see, e.g., A. F.Williams and A. N. Barclay, 1988, Ann. Rev. Immunol. 6:381-405). Thedisplay library can display the antibody as a Fab fragment (e.g., usingtwo polypeptide chains) or a single chain Fv (e.g., using a singlepolypeptide chain). Other formats can also be used.

As in the case of the Fab and other formats, the displayed antibody caninclude one or more constant regions as part of a light and/or heavychain. In one embodiment, each chain includes one constant region, e.g.,as in the case of a Fab. In other embodiments, additional constantregions are displayed.

Antibody libraries can be constructed by a number of processes (see,e.g., de Haard et al., 1999, J. Biol. Chem. 274:18218-30; Hoogenboom etal., 1998, Immunotechnology 4:1-20; and Hoogenboom et al., 2000,Immunol. Today 21:371-378. Further, elements of each process can becombined with those of other processes. The processes can be used suchthat variation is introduced into a single immunoglobulin domain (e.g.,VH or VL) or into multiple immunoglobulin domains (e.g., VH and VL). Thevariation can be introduced into an immunoglobulin variable domain,e.g., in the region of one or more of CDR1, CDR2, CDR3, FR1, FR2, FR3,and FR4, referring to such regions of either and both of heavy and lightchain variable domains. In one embodiment, variation is introduced intoall three CDRs of a given variable domain. In another embodiment, thevariation is introduced into CDR1 and CDR2, e.g., of a heavy chainvariable domain. Any combination is feasible. In one process, antibodylibraries are constructed by inserting diverse oligonucleotides thatencode CDRs into the corresponding regions of the nucleic acid. Theoligonucleotides can be synthesized using monomeric nucleotides ortrinucleotides. For example, Knappik et al., 2000, J. Mol. Biol.296:57-86 describe a method for constructing CDR encodingoligonucleotides using trinucleotide synthesis and a template withengineered restriction sites for accepting the oligonucleotides.

In another process, an animal, e.g., a rodent, is immunized with theFcRn. The animal is optionally boosted with the antigen to furtherstimulate the response. Then spleen cells are isolated from the animal,and nucleic acid encoding VH and/or VL domains is amplified and clonedfor expression in the display library.

In yet another process, antibody libraries are constructed from nucleicacid amplified from naive germline immunoglobulin genes. The amplifiednucleic acid includes nucleic acid encoding the VH and/or VL domain.Sources of immunoglobulin-encoding nucleic acids are described below.Amplification can include PCR, e.g., with primers that anneal to theconserved constant region, or another amplification method.

Nucleic acid encoding immunoglobulin domains can be obtained from theimmune cells of, e.g., a human, a primate, mouse, rabbit, camel, llamaor rodent. In one example, the cells are selected for a particularproperty. B cells at various stages of maturity can be selected. Inanother example, the B cells are naive.

In one embodiment, fluorescent-activated cell sorting (FACS) is used tosort B cells that express surface-bound IgM, IgD, or IgG molecules.Further, B cells expressing different isotypes of IgG can be isolated.In another embodiment, the B or T cell is cultured in vitro. The cellscan be stimulated in vitro, e.g., by culturing with feeder cells or byadding mitogens or other modulatory reagents, such as antibodies toCD40, CD40 ligand or CD20, phorbol myristate acetate, bacteriallipopolysaccharide, concanavalin A, phytohemagglutinin, or pokeweedmitogen.

In still one embodiment, the cells are isolated from a subject that hasan autoimmune disorder, e.g., systemic lupus erythematosus (SLE),rheumatoid arthritis, vasculitis, Sjogren syndrome, systemic sclerosis,or anti-phospholipid syndrome. The subject can be a human, or an animal,e.g., an animal model for the human disease, or an animal having ananalogous disorder. In yet one embodiment, the cells are isolated from atransgenic non-human animal that includes a human immunoglobulin locus.

In one embodiment, the cells have activated a program of somatichypermutation. Cells can be stimulated to undergo somatic mutagenesis ofimmunoglobulin genes, for example, by treatment withanti-immunoglobulin, anti-CD40, and anti-CD38 antibodies (see, e.g.,Bergthorsdottir et al., 2001, J. Immunol. 166:2228). In one embodiment,the cells are naive.

The nucleic acid encoding an immunoglobulin variable domain can beisolated from a natural repertoire by the following exemplary method.First, RNA is isolated from the immune cell. Full length (i.e., capped)mRNAs are separated (e.g., by degrading uncapped RNAs with calfintestinal phosphatase). The cap is then removed with tobacco acidpyrophosphatase and reverse transcription is used to produce the cDNAs.

The reverse transcription of the first (antisense) strand can be done inany manner with any suitable primer. See, e.g., de Haard et al., 1999,J. Biol. Chem. 274:18218-30. The primer binding region can be constantamong different immunoglobulins, e.g., in order to reverse transcribedifferent isotypes of immunoglobulin. The primer binding region can alsobe specific to a particular isotype of immunoglobulin. Typically, theprimer is specific for a region that is 3′ to a sequence encoding atleast one CDR. In one embodiment, poly-dT primers may be used (and maybe preferred for the heavy-chain genes).

A synthetic sequence can be ligated to the 3′ end of the reversetranscribed strand. The synthetic sequence can be used as a primerbinding site for binding of the forward primer during PCR amplificationafter reverse transcription. The use of the synthetic sequence canobviate the need to use a pool of different forward primers to fullycapture the available diversity.

The variable domain-encoding gene is then amplified, e.g., using one ormore rounds. If multiple rounds are used, nested primers can be used forincreased fidelity. The amplified nucleic acid is then cloned into adisplay library vector.

Secondary Screening Methods

After selecting candidate library members that bind to a target, eachcandidate library member can be further analyzed, e.g., to furthercharacterize its binding properties for the target. Each candidatelibrary member can be subjected to one or more secondary screeningassays. The assay can be for a binding property, a catalytic property,an inhibitory property, a physiological property (e.g., cytotoxicity,renal clearance, immunogenicity), a structural property (e.g.,stability, conformation, oligomerization state) or another functionalproperty. The same assay can be used repeatedly, but with varyingconditions, e.g., to determine pH, ionic, or thermal sensitivities.

As appropriate, the assays can use a display library member directly, arecombinant polypeptide produced from the nucleic acid encoding theselected polypeptide, or a synthetic peptide synthesized based on thesequence of the selected polypeptide. Exemplary assays for bindingproperties include the following.

ELISA.

Antibodies selected from an expression library can also be screened fora binding property using an ELISA. For example, each antibody iscontacted to a microtitre plate whose bottom surface has been coatedwith the target, e.g., a limiting amount of the target. The plate iswashed with buffer to remove non-specifically bound polypeptides. Thenthe amount of the antibody bound to the plate is determined by probingthe plate with an antibody that can recognize the test antibody, e.g., atag or constant portion of the antibody. The detection antibody islinked to an enzyme such as alkaline phosphatase or horse radishperoxidase (HRP) which produces a colorimetric product when appropriatesubstrates are provided.

In the case of an antibody from a display library, the antibody can bepurified from cells or assayed in a display library format, e.g., as afusion to a filamentous bacteriophage coat. In another version of theELISA, each antibody selected from an expression library is used to coata different well of a microtitre plate. The ELISA then proceeds using aconstant target molecule to query each well.

Homogeneous Binding Assays.

The binding interaction of candidate antibody with a target can beanalyzed using a homogenous assay, i.e., after all components of theassay are added, additional fluid manipulations are not required. Forexample, fluorescence resonance energy transfer (FRET) can be used as ahomogenous assay (see, for example, Lakowicz et al., U.S. Pat. No.5,631,169; Stavrianopoulos, et al., U.S. Pat. No. 4,868,103). Afluorophore label on the first molecule (e.g., the molecule identifiedin the fraction) is selected such that its emitted fluorescent energycan be absorbed by a fluorescent label on a second molecule (e.g., thetarget) if the second molecule is in proximity to the first molecule.The fluorescent label on the second molecule fluoresces when it absorbsto the transferred energy. Since the efficiency of energy transferbetween the labels is related to the distance separating the molecules,the spatial relationship between the molecules can be assessed. In asituation in which binding occurs between the molecules, the fluorescentemission of the ‘acceptor’ molecule label in the assay should bemaximal. A binding event that is configured for monitoring by FRET canbe conveniently measured through standard fluorometric detection meanswell known in the art (e.g., using a fluorimeter). By titrating theamount of the first or second binding molecule, a binding curve can begenerated to estimate the equilibrium binding constant.

Another example of a homogenous assay is ALPHASCREEN™ (PackardBioscience, Meriden Conn.). ALPHASCREEN™ uses two labeled beads. Onebead generates singlet oxygen when excited by a laser. The other beadgenerates a light signal when singlet oxygen diffuses from the firstbead and collides with it. The signal is only generated when the twobeads are in proximity. One bead can be attached to the display librarymember, the other to the target. Signals are measured to determine theextent of binding.

The homogenous assays can be performed while the candidate polypeptideis attached to the display library vehicle, e.g., a bacteriophage.

Surface Plasmon Resonance (SPR).

The binding interaction of a molecule isolated from an expressionlibrary and a target can be analyzed using SPR. SPR or BiomolecularInteraction Analysis (BIA) detects biospecific interactions in realtime, without labeling any of the interactants. Changes in the mass atthe binding surface (indicative of a binding event) of the BIA chipresult in alterations of the refractive index of light near the surface(the optical phenomenon of surface plasmon resonance (SPR)). The changesin the refractivity generate a detectable signal, which are measured asan indication of real-time reactions between biological molecules.Methods for using SPR are described, for example, in U.S. Pat. No.5,641,640; Raether, 1988, Surface Plasmons Springer Verlag; Sjolanderand Urbaniczky, 1991, Anal. Chem. 63:2338-2345; Szabo et al., 1995,Curr. Opin. Struct. Biol. 5:699-705 and on-line resources provide byBIAcore International AB (Uppsala, Sweden).

Information from SPR can be used to provide an accurate and quantitativemeasure of the equilibrium dissociation constant (K_(d)), and kineticparameters, including K_(on) and K_(off), for the binding of abiomolecule to a target. Such data can be used to compare differentbiomolecules. For example, selected proteins from an expression librarycan be compared to identify proteins that have high affinity for thetarget or that have a slow K_(off). This information can also be used todevelop structure-activity relationships (SAR). For example, the kineticand equilibrium binding parameters of matured versions of a parentprotein can be compared to the parameters of the parent protein. Variantamino acids at given positions can be identified that correlate withparticular binding parameters, e.g., high affinity and slow K_(off).This information can be combined with structural modeling (e.g., usinghomology modeling, energy minimization, or structure determination byx-ray crystallography or NMR). As a result, an understanding of thephysical interaction between the protein and its target can beformulated and used to guide other design processes.

Cellular Assays.

A library of candidate antibodies (e.g., previously identified by adisplay library or otherwise) can be screened for target binding oncells which transiently or stably express and display the target ofinterest on the cell surface. For example, the target can include vectornucleic acid sequences that include segments that encode only theextracellular portion of the polypeptides such that the chimeric targetpolypeptides are produced within the cell, secreted from the cell, orattached to the cell surface through the anchor e.g., in fusion with amembrane anchoring proteins such as Fc. The cell surface expressedtarget can be used for screening antibodies that bind to FcRn and blockthe binding of IgG-Fc. For example, non-specific human IgG-Fc could befluorescently labeled and its binding to FcRn in the presence of absenceof antagonistic antibody can be detected by a change in fluorescenceintensity using flow cytometry e.g., a FACS machine.

Other Methods for Obtaining FcRn-Binding Antibodies

In addition to the use of display libraries, other methods can be usedto obtain a FcRn-binding antibody. For example, the FcRn protein or aregion thereof can be used as an antigen in a non-human animal, e.g., arodent.

In one embodiment, the non-human animal includes at least a part of ahuman immunoglobulin gene. For example, it is possible to engineer mousestrains deficient in mouse antibody production with large fragments ofthe human Ig loci. Using the hybridoma technology, antigen-specificmonoclonal antibodies (Mabs) derived from the genes with the desiredspecificity may be produced and selected. See, e.g., XENOMOUSE™, Greenet al., 1994, Nat. Gen. 7:13-21; U.S. 2003-0070185, WO 96/34096,published Oct. 31, 1996, and PCT Application No. PCT/US96/05928, filedApr. 29, 1996.

In one embodiment, a monoclonal antibody is obtained from the non-humananimal, and then modified, e.g., humanized or deimmunized Winterdescribes a CDR-grafting method that may be used to prepare thehumanized antibodies (UK Patent Application GB 2188638A, filed on Mar.26, 1987; U.S. Pat. No. 5,225,539. All of the CDRs of a particular humanantibody may be replaced with at least a portion of a non-human CDR oronly some of the CDRs may be replaced with non-human CDRs. It is onlynecessary to replace the number of CDRs required for binding of thehumanized antibody to a predetermined antigen.

Humanized antibodies can be generated by replacing sequences of the Fvvariable region that are not directly involved in antigen binding withequivalent sequences from human Fv variable regions. General methods forgenerating humanized antibodies are provided by Morrison, S. L., 1985,Science 229:1202-1207, by Oi et al., 1986, BioTechniques 4:214, and byQueen et al. U.S. Pat. No. 5,585,089, U.S. Pat. No. 5,693,761 and U.S.Pat. No. 5,693,762. Those methods include isolating, manipulating, andexpressing the nucleic acid sequences that encode all or part ofimmunoglobulin Fv variable regions from at least one of a heavy or lightchain. Sources of such nucleic acid are well known to those skilled inthe art and, for example, may be obtained from a hybridoma producing anantibody against a predetermined target, as described above. Therecombinant DNA encoding the humanized antibody, or fragment thereof,can then be cloned into an appropriate expression vector.

An FcRn-binding antibody may also be modified by specific deletion ofhuman T cell epitopes or “deimmunization” by the methods disclosed in WO98/52976 and WO 00/34317, the contents of which are specificallyincorporated by reference herein. Briefly, the heavy and light chainvariable regions of an antibody can be analyzed for peptides that bindto MHC Class II; these peptides represent potential T-cell epitopes (asdefined in WO 98/52976 and WO 00/34317). For detection of potentialT-cell epitopes, a computer modeling approach termed “peptide threading”can be applied, and in addition a database of human MHC class II bindingpeptides can be searched for motifs present in the VH and VL sequences,as described in WO 98/52976 and WO 00/34317. These motifs bind to any ofthe 18 major MHC class II DR allotypes, and thus constitute potential Tcell epitopes. Potential T-cell epitopes detected can be eliminated bysubstituting small numbers of amino acid residues in the variableregions or by single amino acid substitutions. As far as possibleconservative substitutions are made, often but not exclusively, an aminoacid common at this position in human germline antibody sequences may beused. Human germline sequences are disclosed in Tomlinson, I. A. et al.,1992, J. Mol. Biol. 227:776-798; Cook, G. P. et al., 1995, Immunol.Today Vol. 16 (5): 237-242; Chothia, D. et al., 1992, J. Mol. Bio.227:799-817. The V BASE directory provides a comprehensive directory ofhuman immunoglobulin variable region sequences (compiled by Tomlinson,I. A. et al. MRC Centre for Protein Engineering, Cambridge, UK). Afterthe deimmunizing changes are identified, nucleic acids encoding V_(H)and V_(L) can be constructed by mutagenesis or other synthetic methods(e.g., de novo synthesis, cassette replacement, and so forth).Mutagenized variable sequence can, optionally, be fused to a humanconstant region, e.g., human IgG1 or K constant regions.

In some cases, a potential T cell epitope will include residues whichare known or predicted to be important for antibody function. Forexample, potential T cell epitopes are usually biased towards the CDRs.In addition, potential T cell epitopes can occur in framework residuesimportant for antibody structure and binding. Changes to eliminate thesepotential epitopes will in some cases require more scrutiny, e.g., bymaking and testing chains with and without the change. Where possible,potential T cell epitopes that overlap the CDRs were eliminated bysubstitutions outside the CDRs. In some cases, an alteration within aCDR is the only option, and thus variants with and without thissubstitution should be tested. In other cases, the substitution requiredto remove a potential T cell epitope is at a residue position within theframework that might be critical for antibody binding. In these cases,variants with and without this substitution should be tested. Thus, insome cases several variant deimmunized heavy and light chain variableregions were designed and various heavy/light chain combinations testedin order to identify the optimal deimmunized antibody. The choice of thefinal deimmunized antibody can then be made by considering the bindingaffinity of the different variants in conjunction with the extent ofdeimmunization, i.e., the number of potential T cell epitopes remainingin the variable region. Deimmunization can be used to modify anyantibody, e.g., an antibody that includes a non-human sequence, e.g., asynthetic antibody, a murine antibody other non-human monoclonalantibody, or an antibody isolated from a display library.

Germlining Antibodies.

An antibody used to treat an IgG-mediated autoimmune disease can be usedfor multiple administrations. Precautions that would lower theimmunogenicity of the therapeutic antibody include reverting one or morenon-germline amino acids in framework regions to corresponding germlineamino acids (e.g., so long as binding properties are substantiallyretained) of the antibody (especially of Fabs).

It is possible to modify an antibody that binds FcRn, e.g., an antibodydescribed herein, in order to make the variable regions of the antibodymore similar to one or more germline sequences. For example, an antibodycan include one, two, three, or more amino acid substitutions, e.g., ina framework, CDR, or constant region, to make it more similar to areference germline sequence. One exemplary germlining method can includeidentifying one or more germline sequences that are similar (e.g., mostsimilar in a particular database) to the sequence of the isolatedantibody. Mutations (at the amino acid level) can then be made in theisolated antibody, either incrementally or in combination with othermutations. For example, a nucleic acid library that includes sequencesencoding some or all possible germline mutations is made. The mutatedantibodies are then evaluated, e.g., to identify an antibody that hasone or more additional germline residues relative to the isolatedantibody and that is still useful (e.g., has a functional activity). Inone embodiment, as many germline residues are introduced into anisolated antibody as possible.

In one embodiment, mutagenesis is used to substitute or insert one ormore germline residues into a framework and/or constant region. Forexample, a germline framework and/or constant region residue can be froma germline sequence that is similar (e.g., most similar) to thenon-variable region being modified. After mutagenesis, activity (e.g.,binding or other functional activity) of the antibody can be evaluatedto determine if the germline residue or residues are tolerated (i.e., donot abrogate activity) Similar mutagenesis can be performed in theframework regions.

Selecting a germline sequence can be performed in different ways. Forexample, a germline sequence can be selected if it meets a predeterminedcriteria for selectivity or similarity, e.g., at least a certainpercentage identity, e.g., at least 75, 80, 85, 90, 91, 92, 93, 94, 95,96, 97, 98, 99, or 99.5% identity. The selection can be performed usingat least 2, 3, 5, or 10 germline sequences. In the case of CDR1 andCDR2, identifying a similar germline sequence can include selecting onesuch sequence. In the case of CDR3, identifying a similar germlinesequence can include selecting one such sequence, but may includingusing two germline sequences that separately contribute to theamino-terminal portion and the carboxy-terminal portion. In otherimplementations more than one or two germline sequences are used, e.g.,to form a consensus sequence.

In one embodiment, with respect to a particular reference variabledomain sequence, e.g., a sequence described herein, a related variabledomain sequence has at least 30, 40, 50, 60, 70, 80, 90, 95 or 100% ofthe CDR amino acid positions that are not identical to residues in thereference CDR sequences, residues that are identical to residues atcorresponding positions in a human germline sequence (i.e., an aminoacid sequence encoded by a human germline nucleic acid).

In one embodiment, with respect to a particular reference variabledomain sequence, e.g., a sequence described herein, a related variabledomain sequence has at least 30, 50, 60, 70, 80, 90 or 100% of the FRregions are identical to FR sequence from a human germline sequence,e.g., a germline sequence related to the reference variable domainsequence.

Accordingly, it is possible to isolate an antibody which has similaractivity to a given antibody of interest, but is more similar to one ormore germline sequences, particularly one or more human germlinesequences. For example, an antibody can be at least 90, 91, 92, 93, 94,95, 96, 97, 98, 99, or 99.5% identical to a germline sequence in aregion outside the CDRs (e.g., framework regions). Further, an antibodycan include at least 1, 2, 3, 4, or 5 germline residues in a CDR region,the germline residue being from a germline sequence of similar (e.g.,most similar) to the variable region being modified. Germline sequencesof primary interest are human germline sequences. The activity of theantibody (e.g., the binding activity) can be within a factor or 100, 10,5, 2, 0.5, 0.1, and 0.001 of the original antibody.

Exemplary germline reference sequences for V_(kappa) include: O12/O2,O18/O8, A20, A30, L14, L1, L15, L4/18a, L5/L19, L8, L23, L9, L24, L11,L12, O11/O1, A17, A1, A18, A2, A19/A3, A23, A27, A11, L2/L16, L6, L20,L25, B3, B2, A26/A10, and A14. See, e.g., Tomlinson et al., 1995, EMBOJ. 14(18):4628-3.

A germline reference sequence for the HC variable domain can be based ona sequence that has particular canonical structures, e.g., 1-3structures in the H1 and H2 hypervariable loops. The canonicalstructures of hypervariable loops of an immunoglobulin variable domaincan be inferred from its sequence, as described in Chothia et al., 1992,J. Mol. Biol. 227:799-817; Tomlinson et al., 1992, J. Mol. Biol.227:776-798); and Tomlinson et al., 1995, EMBO J. 14(18):4628-38.Exemplary sequences with a 1-3 structure include: DP-1, DP-8, DP-12,DP-2, DP-25, DP-15, DP-7, DP-4, DP-31, DP-32, DP-33, DP-35, DP-40, 7-2,hv3005, hv3005f3, DP-46, DP-47, DP-58, DP-49, DP-50, DP-51, DP-53, andDP-54.

Ligand Production

Standard recombinant nucleic acid methods can be used to express anantibody that binds to FcRn. Generally, a nucleic acid sequence encodingthe antibody is cloned into a nucleic acid expression vector. Of course,if the antibody includes multiple polypeptide chains, each chain can becloned into an expression vector, e.g., the same or different vectors,that are expressed in the same or different cells.

Antibody Production.

Some antibodies, e.g., Fabs, can be produced in bacterial cells, e.g.,E. coli cells. For example, if the Fab is encoded by sequences in aphage display vector that includes a suppressible stop codon between thedisplay entity and a bacteriophage protein (or fragment thereof), thevector nucleic acid can be transferred into a bacterial cell that cannotsuppress a stop codon. In this case, the Fab is not fused to the geneIII protein and is secreted into the periplasm and/or media.

Antibodies can also be produced in eukaryotic cells. In one embodiment,the antibodies (e.g., scFv's) are expressed in a yeast cell such asPichia (see, e.g., Powers et al., 2001, J. Immunol. Methods.251:123-35), Hanseula, or Saccharomyces.

In one embodiment, antibodies are produced in mammalian cells. Mammalianhost cells for expressing the clone antibodies or antigen-bindingfragments thereof include Chinese Hamster Ovary (CHO cells) (includingdhfr-CHO cells, described in Urlaub and Chasin, 1980, Proc. Natl. Acad.Sci. USA 77:4216-4220, used with a DHFR selectable marker, e.g., asdescribed in Kaufman and Sharp, 1982, Mol. Biol. 159:601 621),lymphocytic cell lines, e.g., NS0 myeloma cells and SP2 cells, COScells, and a cell from a transgenic animal, e.g., a transgenic mammal.For example, the cell is a mammary epithelial cell.

In addition to the nucleic acid sequence encoding the diversifiedimmunoglobulin domain, the recombinant expression vectors may carryadditional sequences, such as sequences that regulate replication of thevector in host cells (e.g., origins of replication) and selectablemarker genes. The selectable marker gene facilitates selection of hostcells into which the vector has been introduced (see e.g., U.S. Pat.Nos. 4,399,216, 4,634,665 and 5,179,017). For example, typically theselectable marker gene confers resistance to drugs, such as G418,hygromycin or methotrexate, on a host cell into which the vector hasbeen introduced. Selectable marker genes include the dihydrofolatereductase (DHFR) gene (for use in dhfr⁻ host cells with methotrexateselection/amplification) and the neo gene (for G418 selection).

In an exemplary system for recombinant expression of an antibody, orantigen-binding portion thereof, a recombinant expression vectorencoding both the antibody heavy chain and the antibody light chain isintroduced into dhfr⁻ CHO cells by calcium phosphate-mediatedtransfection. Within the recombinant expression vector, the antibodyheavy and light chain genes are each operatively linked toenhancer/promoter regulatory elements (e.g., derived from SV40, CMV,adenovirus and the like, such as a CMV enhancer/AdMLP promoterregulatory element or an SV40 enhancer/AdMLP promoter regulatoryelement) to drive high levels of transcription of the genes. Therecombinant expression vector also carries a DHFR gene, which allows forselection of CHO cells that have been transfected with the vector usingmethotrexate selection/amplification. The selected transformant hostcells are cultured to allow for expression of the antibody heavy andlight chains and intact antibody is recovered from the culture medium.Standard molecular biology techniques are used to prepare therecombinant expression vector, transfect the host cells, select fortransformants, culture the host cells and recover the antibody from theculture medium. For example, some antibodies can be isolated by affinitychromatography with a Protein A or Protein G coupled matrix.

For antibodies that include an Fc domain, the antibody production systemmay produce antibodies in which the Fc region is glycosylated. Forexample, the Fc domain of IgG molecules is glycosylated at asparagine297 in the CH2 domain. This asparagine is the site for modification withbiantennary-type oligosaccharides. It has been demonstrated that thisglycosylation is required for effector functions mediated by Fcgreceptors and complement Clq (Burton and Woof, 1992, Adv. Immunol.51:1-84; Jefferis et al., 1998, Immunol. Rev. 163:59-76). In oneembodiment, the Fc domain is produced in a mammalian expression systemthat appropriately glycosylates the residue corresponding to asparagine297. The Fc domain can also include other eukaryotic post-translationalmodifications.

Antibodies can also be produced by a transgenic animal. For example,U.S. Pat. No. 5,849,992 describes a method of expressing an antibody inthe mammary gland of a transgenic mammal A transgene is constructed thatincludes a milk-specific promoter and nucleic acids encoding theantibody of interest and a signal sequence for secretion. The milkproduced by females of such transgenic mammals includes,secreted-therein, the antibody of interest. The antibody can be purifiedfrom the milk, or for some applications, used directly.

One method for producing a transgenic mouse is as follows. Briefly, atargeting construct that encodes the antibody is microinjected into themale pronucleus of fertilized oocytes. The oocytes are injected into theuterus of a pseudopregnant foster mother for the development into viablepups. Some offspring incorporate the transgene.

Assay Systems for FcRn Candidate Antibodies

FcRn candidate antibodies can be further characterized in assays thatmeasure their modulatory activity toward FcRn or fragments thereof invitro or in vivo. For example, FcRn can be combined with a substratesuch as non-specific IgG or Fc portion of the IgG or albumin under assayconditions permitting reaction of the FcRn with the substrate. The assayis performed in the absence of the FcRn candidate antibody, and in thepresence of increasing concentrations of the FcRn candidate antibody.The concentration of candidate antibody at which 50% of the FcRnactivity (e.g., binding to the substrate) is inhibited by the candidateantibody is the IC₅₀ value (Inhibitory Concentration 50%) or EC₅₀(Effective Concentration 50%) value for that antibody. Within a seriesor group of candidate antibodies, those having lower IC₅₀ or EC₅₀ valuesare considered more potent inhibitors of FcRn than those antibodieshaving higher IC₅₀ or EC₅₀ values. In some embodiments, antibodies havean IC₅₀ value of 800 nM, 400 nM, 100 nM, 25 nM, 5 nM, 1 nM, or less asmeasured in an in vitro assay for inhibition of FcRn activity.

The candidate antibodies can also be evaluated for selectivity towardFcRn. For example, a FcRn candidate antibody can be assayed for itspotency toward FcRn and a panel of cell surface receptors, such asreceptors that also utilize the β2M domain, and an IC₅₀ value or EC₅₀value can be determined for each receptor protein. In one embodiment, acompound that demonstrates a low IC₅₀ value or EC₅₀ value for the FcRn,and a higher IC₅₀ value or EC₅₀ value for other receptors within thetest panel (e.g., MHC class I molecules) is considered to be selectivetoward FcRn.

Ex vivo endothelial cells or epithelial cells expressing the endogenousFcRn could be used to follow the endocytosis or transcytosis of thecandidate antibodies under different pH and temperature conditions. IgGtranscytosis or recycling by FcRn can be measured by following a labeledantibody in the presence or absence of various chemicals and underdifferent conditions that are known to influence or affect theintracellular trafficking pathway.

A pharmacokinetics study in rat, mice, or monkey could be performed withpH dependent and independent FcRn binding antibodies for determiningtheir half-life in the serum. Likewise, the protective effect of theantibody can be assessed in vivo for potential use in immunomodulatingtherapy or as an salvage immunotherapy by injecting the antibody in thepresence or absence of a labeled IgG or the labeled Fc portion of theIgG. A decrease in the half-life of the labeled IgG/Fc in the presenceof the candidate antibody is an indication of the therapeutic efficacyof the antibody.

Pharmaceutical Compositions

In another aspect, the disclosure provides compositions, e.g.,pharmaceutically acceptable compositions or pharmaceutical compositions,which include an FcRn-binding antibody. The FcRn-binding antibody can beformulated together with a pharmaceutically acceptable carrier.Pharmaceutical compositions include therapeutic compositions anddiagnostic compositions, e.g., compositions that include labeledFcRn-binding antibodies for in vivo imaging.

A pharmaceutically acceptable carrier includes any and all solvents,dispersion media, coatings, antibacterial and antifungal agents,isotonic and absorption delaying agents, and the like that arephysiologically compatible. Preferably, the carrier is suitable forintravenous, intramuscular, subcutaneous, parenteral, spinal, orepidermal administration (e.g., by injection or infusion). Depending onthe route of administration, the FcRn-binding antibody may be coated ina material to protect the compound from the action of acids and othernatural conditions that may inactivate the compound.

A pharmaceutically acceptable salt is a salt that retains the desiredbiological activity of the parent compound and does not impart anyundesired toxicological effects (see e.g., Berge, S. M., et al., 1977,J. Pharm. Sci. 66:1-19). Examples of such salts include acid additionsalts and base addition salts. Acid addition salts include those derivedfrom nontoxic inorganic acids, such as hydrochloric, nitric, phosphoric,sulfuric, hydrobromic, hydroiodic, phosphorous, and the like, as well asfrom nontoxic organic acids such as aliphatic mono- and dicarboxylicacids, phenyl-substituted alkanoic acids, hydroxy alkanoic acids,aromatic acids, aliphatic and aromatic sulfonic acids, and the like.Base addition salts include those derived from alkaline earth metals,such as sodium, potassium, magnesium, calcium, and the like, as well asfrom nontoxic organic amines, such as N,N′-dibenzylethylenediamine,N-methylglucamine, chloroprocaine, choline, diethanolamine,ethylenediamine, procaine, and the like.

The compositions may be in a variety of forms. These include, forexample, liquid, semi-solid and solid dosage forms, such as liquidsolutions (e.g., injectable and infusible solutions), dispersions orsuspensions, tablets, pills, powders, liposomes and suppositories. Theform can depend on the intended mode of administration and therapeuticapplication. Many compositions are in the form of injectable orinfusible solutions, such as compositions similar to those used foradministration of humans with antibodies. An exemplary mode ofadministration is parenteral (e.g., intravenous, subcutaneous,intraperitoneal, intramuscular). In one embodiment, the FcRn-bindingantibody is administered by intravenous infusion or injection. Inanother embodiment, the FcRn-binding antibody is administered byintramuscular or subcutaneous injection.

The composition can be formulated as a solution, microemulsion,dispersion, liposome, or other ordered structure suitable to high drugconcentration. Sterile injectable solutions can be prepared byincorporating the active compound (i.e., the ligand) in the requiredamount in an appropriate solvent with one or a combination ofingredients enumerated above, as required, followed by filteredsterilization. Generally, dispersions are prepared by incorporating theactive compound into a sterile vehicle that contains a basic dispersionmedium and the required other ingredients from those enumerated above.In the case of sterile powders for the preparation of sterile injectablesolutions, the methods of preparation are vacuum drying andfreeze-drying that yields a powder of the active ingredient plus anyadditional desired ingredient from a previously sterile-filteredsolution thereof. The proper fluidity of a solution can be maintained,for example, by the use of a coating such as lecithin, by themaintenance of the required particle size in the case of dispersion andby the use of surfactants. Prolonged absorption of injectablecompositions can be brought about by including in the composition anagent that delays absorption, for example, monostearate salts andgelatin.

An FcRn-binding antibody can be administered by a variety of methodsknown in the art, although for many applications, the route/mode ofadministration is intravenous injection or infusion. For example, fortherapeutic applications, the FcRn-binding antibody can be administeredby intravenous infusion at a rate of less than 30, 20, 10, 5, or 1mg/min to reach a dose of about 1 to 100 mg/m² or 7 to 25 mg/m². Theroute and/or mode of administration will vary depending upon the desiredresults. In certain embodiments, the active compound may be preparedwith a carrier that will protect the compound against rapid release,such as a controlled release formulation, including implants, andmicroencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Manymethods for the preparation of such formulations are patented orgenerally known. See, e.g., Sustained and Controlled Release DrugDelivery Systems, J. R. Robinson, ed., 1978, Marcel Dekker, Inc., NewYork.

In certain embodiments, the antibody may be orally administered, forexample, with an inert diluent or an assimilable edible carrier. Thecompound (and other ingredients, if desired) may also be enclosed in ahard or soft shell gelatin capsule, compressed into tablets, orincorporated directly into the subject's diet. For oral therapeuticadministration, the compounds may be incorporated with excipients andused in the form of ingestible tablets, buccal tablets, troches,capsules, elixirs, suspensions, syrups, wafers, and the like. Toadminister a compound disclosed herein by other than parenteraladministration, it may be necessary to coat the compound with, orco-administer the compound with, a material to prevent its inactivation.

Pharmaceutical compositions can be administered with medical devicesknown in the art. For example, in one embodiment, a pharmaceuticalcomposition disclosed herein can be administered with a device, e.g., aneedleless hypodermic injection device, a pump, or implant.

In certain embodiments, an FcRn-binding antibody can be formulated toensure proper distribution in vivo. For example, the blood-brain barrier(BBB) excludes many highly hydrophilic compounds. To ensure that thetherapeutic compounds disclosed herein cross the BBB (if desired), theycan be formulated, for example, in liposomes. For methods ofmanufacturing liposomes, see, e.g., U.S. Pat. Nos. 4,522,811; 5,374,548;and 5,399,331. The liposomes may comprise one or more moieties that areselectively transported into specific cells or organs, thus enhancetargeted drug delivery (see, e.g., V. V. Ranade, 1989, J. Clin.Pharmacol. 29:685).

Dosage regimens are adjusted to provide the optimum desired response(e.g., a therapeutic response). For example, a single bolus may beadministered, several divided doses may be administered over time or thedose may be proportionally reduced or increased as indicated by theexigencies of the therapeutic situation. It is especially advantageousto formulate parenteral compositions in dosage unit form for ease ofadministration and uniformity of dosage. Dosage unit form as used hereinrefers to physically discrete units suited as unitary dosages for thesubjects to be treated; each unit contains a predetermined quantity ofactive compound calculated to produce the desired therapeutic effect inassociation with the required pharmaceutical carrier. The specificationfor the dosage unit forms can be dictated by and directly dependent on(a) the unique characteristics of the active compound and the particulartherapeutic effect to be achieved, and (b) the limitations inherent inthe art of compounding such an active compound for the treatment ofsensitivity in individuals.

An exemplary, non-limiting range for a therapeutically orprophylactically effective amount of an antibody disclosed herein is0.1-20 mg/kg, or 1-10 mg/kg. An anti-FcRn antibody can be administered,e.g., by intravenous infusion, e.g., at a rate of less than 30, 20, 10,5, or 1 mg/min to reach a dose of about 1 to 100 mg/m² or about 5 to 30mg/m². Dosage values may vary with the type and severity of thecondition to be alleviated. For a particular subject, specific dosageregimens can be adjusted over time according to the individual need andthe professional judgment of the person administering or supervising theadministration of the compositions.

The pharmaceutical compositions disclosed herein may include atherapeutically effective amount or a prophylactically effective amountof an FcRn-binding antibody disclosed herein. A “therapeuticallyeffective amount” refers to an amount effective, at dosages and forperiods of time necessary, to achieve the desired therapeutic result. Atherapeutically effective amount of the composition may vary accordingto factors such as the disease state, age, sex, and weight of theindividual, and the ability of the antibody to elicit a desired responsein the individual. A therapeutically effective amount is also one inwhich any toxic or detrimental effects of the composition is outweighedby the therapeutically beneficial effects.

Stabilization and Retention

In one embodiment, an FcRn-binding antibody is physically associatedwith a moiety that improves its stabilization and/or retention incirculation, e.g., in blood, serum, lymph, or other tissues, e.g., by atleast 1.5, 2, 5, 10, or 50 fold. For example, an FcRn-binding antibodycan be associated with a polymer, e.g., a substantially non-antigenicpolymers, such as polyalkylene oxides or polyethylene oxides. Suitablepolymers will vary substantially by weight. Polymers having molecularnumber average weights ranging from about 200 to about 35,000 (or about1,000 to about 15,000, and 2,000 to about 12,500) can be used. Forexample, an FcRn-binding antibody can be conjugated to a water solublepolymer, e.g., hydrophilic polyvinyl polymers, e.g. polyvinylalcohol andpolyvinylpyrrolidone. A non-limiting list of such polymers includepolyalkylene oxide homopolymers such as polyethylene glycol (PEG) orpolypropylene glycols, polyoxyethylenated polyols, copolymers thereofand block copolymers thereof, provided that the water solubility of theblock copolymers is maintained.

Kits

An FcRn-binding antibody described herein can be provided in a kit,e.g., as a component of a kit. For example, the kit includes (a) anFcRn-binding antibody, e.g., a composition that includes an FcRn-bindingantibody, and, optionally (b) informational material. The informationalmaterial can be descriptive, instructional, marketing or other materialthat relates to the methods described herein and/or the use of anFcRn-binding antibody for the methods described herein.

The informational material of the kits is not limited in its form. Inone embodiment, the informational material can include information aboutproduction of the compound, molecular weight of the compound,concentration, date of expiration, batch or production site information,and so forth. In one embodiment, the informational material relates tousing the antibody to treat, prevent, or diagnosis a disorder describedherein, e.g., an autoimmune disorder.

In one embodiment, the informational material can include instructionsto administer an FcRn-binding antibody in a suitable manner to performthe methods described herein, e.g., in a suitable dose, dosage form, ormode of administration (e.g., a dose, dosage form, or mode ofadministration described herein). In one embodiment, the informationalmaterial can include instructions to administer an FcRn-binding antibodyto a suitable subject, e.g., a human, e.g., a human having, or at riskfor, an autoimmune disorder (e.g., rheumatoid arthritis or systemiclupus erythematosis). For example, the material can include instructionsto administer an FcRn-binding antibody to a patient with lupus or apatient with another autoimmune disorder.

The informational material of the kits is not limited in its form. Inmany cases, the informational material, e.g., instructions, is providedin printed matter, e.g., a printed text, drawing, and/or photograph,e.g., a label or printed sheet. However, the informational material canalso be provided in other formats, such as computer readable material,video recording, or audio recording. In one embodiment, theinformational material of the kit is contact information, e.g., aphysical address, email address, website, or telephone number, where auser of the kit can obtain substantive information about an FcRn-bindingantibody and/or its use in the methods described herein. Of course, theinformational material can also be provided in any combination offormats.

In addition to an FcRn-binding antibody, the composition of the kit caninclude other ingredients, such as a solvent or buffer, a stabilizer, apreservative, a flavoring agent (e.g., a bitter antagonist or asweetener), a fragrance or other cosmetic ingredient, and/or a secondagent for treating an autoimmune disorder described herein, e.g.,rheumatoid arthritis or systemic lupus erythematosis. Alternatively, theother ingredients can be included in the kit, but in differentcompositions or containers than an FcRn-binding antibody. In suchembodiments, the kit can include instructions for admixing anFcRn-binding antibody and the other ingredients, or for using anFcRn-binding antibody together with the other ingredients.

An FcRn-binding antibody can be provided in any form, e.g., liquid,dried or lyophilized form. It is preferred that an FcRn-binding antibodybe substantially pure and/or sterile. When an FcRn-binding antibody isprovided in a liquid solution, the liquid solution preferably is anaqueous solution, with a sterile aqueous solution being preferred. Whenan FcRn-binding antibody is provided as a dried form, reconstitutiongenerally is by the addition of a suitable solvent. The solvent, e.g.,sterile water or buffer, can optionally be provided in the kit.

The kit can include one or more containers for the compositioncontaining an FcRn-binding antibody. In some embodiments, the kitcontains separate containers, dividers or compartments for thecomposition and informational material. For example, the composition canbe contained in a bottle, vial, or syringe, and the informationalmaterial can be contained in a plastic sleeve or packet. In otherembodiments, the separate elements of the kit are contained within asingle, undivided container. For example, the composition is containedin a bottle, vial or syringe that has attached thereto the informationalmaterial in the form of a label. In some embodiments, the kit includes aplurality (e.g., a pack) of individual containers, each containing oneor more unit dosage forms (e.g., a dosage form described herein) of anFcRn-binding antibody. For example, the kit includes a plurality ofsyringes, ampules, foil packets, or blister packs, each containing asingle unit dose of an FcRn-binding antibody. The containers of the kitscan be air tight, waterproof (e.g., impermeable to changes in moistureor evaporation), and/or light-tight.

The kit optionally includes a device suitable for administration of thecomposition, e.g., a syringe, inhalant, pipette, forceps, measuredspoon, dropper (e.g., eye dropper), swab (e.g., a cotton swab or woodenswab), or any such delivery device. In one embodiment, the device is animplantable device that dispenses metered doses of the antibody. Thedisclosure also features a method of providing a kit, e.g., by combiningcomponents described herein.

Treatments

Antibodies that bind to FcRn and identified by the method describedherein and/or detailed herein have therapeutic and prophylacticutilities. These antibodies can be administered to a subject to treat,prevent, and/or diagnose a variety of disorders, including autoimmunedisorders, or even to cells in culture, e.g., in vitro or ex vivo.

The term “treating” refers to administering a therapy in an amount,manner, and/or mode effective to improve a condition, symptom, orparameter associated with a disorder or to prevent progression of adisorder, to either a statistically significant degree or to a degreedetectable to one skilled in the art. An effective amount, manner, ormode can vary depending on the subject and may be tailored to thesubject. The subject can be a human or a non-human animal, e.g., anon-human mammal.

The FcRn-binding antibody can be administered in a therapeuticallyeffective amount, e.g., such that upon single or multiple doseadministration to a subject, the subject exhibits an amelioration ofsymptoms of a disorder, e.g., an autoimmune disorder (e.g., rheumatoidarthritis or systemic lupus erythematosis) or of a parameter indicativeof presence or risk for the disorder.

Exemplary disorders which affect many organs or localized organs in thebody include: Multiple Sclerosis, rheumatoid arthritis, inflammatorybowel diseases (IBD), lupus, and ankylosing spondylitis. Some of thesedisorders are discussed below. In one aspect, the invention providesmethods for the treatment of cancer. Still other disorders that can betreated using an FcRn-binding antibody include: scleroderma, Sjogren'ssyndrome, Goodpasture's syndrome, Wegener's granulomatosis, polymyalgiarheumatica, temporal arteritis/gian cell arteritis, alopecia greata,anklosing spondylitis, antiphospholipid syndrome, autoimmune Addison'sdisease, autoimmune hemolytic anemia, autoimmune hepatitis, autoimmuneinner ear disease, autoimmune lymphoproliferative syndrome (ALPS),autoimmune thrombocytopenic purpura (ATP), Behcet's disease, bullouspemphigoid, cardiomyopathy, celiac sprue-dermatitis, chronic fatiguesyndrome immune deficiency syndrome (CFIDS), chronic inflammatorydemyelinating polyneuropathy, cicatricial pemphigoid, cold agglutinindisease, CREST Syndrome, Crohn's disease, Dego's disease,dermatomyositis, juvenile dermatomyositis, discoid lupus, essentialmixed cryoglobulinemia, fibromyalgia, fibromyositis, Grave's disease,Guillain-Barre syndrome, Hashimoto's thyroiditis, idiopathic pulmonaryfibrosis, idiopathic thrombocytopenia purpura (ITP), IgA nephropathy,insulin dependent diabetes (Type I), juvenile arthritis, Meniere'sdisease, mixed connective tissue disease, myasthenia gravis, pemphigusvulgaris, pemphigus foliaceus, paraneoplastic pemphigus, perniciousanemia, polyarteritis nodosa, polychondritis, polyglancular syndromes,polymyalgia rheumatica, polymyositis, dermatomyositis, primaryagammaglobulinemia, primary biliary cirrhosis, psoriasis, Raynaud'sphenomenon, Reiter's syndrome, rheumatic fever, sarcoidosis, stiff-mansyndrome, Takayasu arteritis, ulcerative colitis, uveitis, vasculitis,vitiligo.

In some embodiments, the anti-FcRn binding antibody is administered toremove an unwanted therapeutic antibody from the bloodstream.

In some embodiments, the anti-FcRn binding antibody is administered tosuppress the level of anti-HLA antibodies. In some embodiments the levelof anti-HLA antibodies is suppressed in connection with organtransplant.

Methods of administering FcRn-binding antibodies are described in“Pharmaceutical Compositions.” Suitable dosages of the molecules usedwill depend on the age and weight of the subject and the particular drugused. The antibodies can be used as competitive agents to inhibit orreduce an undesirable interaction, e.g., between a natural orpathological agent and the FcRn.

The FcRn binding antibody can be used to deliver macro andmicromolecules, e.g., a gene into the cell for gene therapy purposesinto the endothelium or epithelium and target only those tissuesexpressing the FcRn. The antibodies may be used to deliver a variety ofcytotoxic drugs including therapeutic drugs, a compound emittingradiation, molecules of plants, fungal, or bacterial origin, biologicalproteins, and mixtures thereof. The cytotoxic drugs can beintracellularly acting cytotoxic drugs, such as short range radiationemitters, including, for example, short range, high energy α-emitters,as described herein.

In the case of polypeptide toxins, recombinant nucleic acid techniquescan be used to construct a nucleic acid that encodes the antibody andthe cytotoxin (or a polypeptide component thereof) as translationalfusions. The recombinant nucleic acid is then expressed, e.g., in cellsand the encoded fusion polypeptide isolated.

Alternatively, the FcRn-binding antibody can be coupled to high energyradiation emitters, for example, a radioisotope, such as ¹³¹I,a.gamma.-emitter, which, when localized at a site, results in a killingof several cell diameters. See, e.g., S. E. Order, “Analysis, Results,and Future Prospective of the Therapeutic Use of Radiolabeled Antibodyin Cancer Therapy”, Monoclonal Antibodies for Cancer Detection andTherapy, R. W. Baldwin et al. (eds.), pp 303 316 (Academic Press 1985).Other suitable radioisotopes include a emitters, such as ²¹²Bi, ²¹³Bi,and ²¹¹At, and b emitters, such as ¹⁸⁶Re and ⁹⁰Y. Moreover, ¹⁷⁷Lu mayalso be used as both an imaging and cytotoxic agent.

Radioimmunotherapy (RIT) using antibodies labeled with ¹³¹I, ⁹⁰Y and¹⁷⁷Lu is under intense clinical investigation. There are significantdifferences in the physical characteristics of these three nuclides andas a result, the choice of radionuclide is very critical in order todeliver maximum radiation dose to a tissue of interest. The higher betaenergy particles of ⁹⁰Y may be good for bulky tumors. The relatively lowenergy beta particles of ¹³¹I are ideal, but in vivo dehalogenation ofradioiodinated molecules is a major disadvantage for internalizingantibody. In contrast, ¹⁷⁷Lu has low energy beta particle with only0.2-0.3 mm range and delivers much lower radiation dose to bone marrowcompared to ⁹⁰Y. In addition, due to longer physical half-life (comparedto ⁹⁰Y), the residence times are higher. As a result, higher activities(more mCi amounts) of ¹⁷⁷Lu labeled agents can be administered withcomparatively less radiation dose to marrow. There have been severalclinical studies investigating the use of ¹⁷⁷Lu labeled antibodies inthe treatment of various cancers. (Mulligan T et al., 1995, Clin. Canc.Res. 1: 1447-1454; Meredith R F, et al., 1996, J. Nucl. Med.37:1491-1496; Alvarez R D, et al., 1997, Gynecol. Oncol. 65: 94-101).

Use of the therapeutic methods to treat autoimmunity has a number ofbenefits. Since the antibodies specifically recognize FcRn, other tissueis spared and high levels of the agent are delivered directly to thesite where therapy is required. Treatment can be effectively monitoredwith clinical parameters. Alternatively, these parameters can be used toindicate when such treatment should be employed.

An FcRn-binding antibody can be administered in combination with one ormore of the existing modalities for treating autoimmune disordersincluding, but not limited to: intravenous Ig therapy, nonsteroidalanti-inflammatory drugs (NSAID), and corticosteroids; andanti-inflammatory treatments such as cyclosporins, rapamycins orascomycins, or their immunosuppressive analogs, e.g., cyclosporin A,cyclosporin G, FK-506, rapamycin, 40-O-(2-hydroxy)ethyl-rapamycin etc.;cyclophosphamide; azathioprene; methotrexate; brequinar; FTY 720;leflunomide; mnizoribine; mycophenolic acid; mycophenolate mofetil;15-deoxyspergualine; immunosuppressive monoclonal antibodies, e.g.,monoclonal antibodies to leukocyte receptors, e.g., MHC, CD2, CD3, CD4,CD7, CD25, CD28, B7, CD45, or CD58 or their ligands; or otherimmunomodulatory compounds, e.g., CTLA4Ig, or other adhesion moleculeinhibitors, e.g. mAbs or low molecular weight inhibitors includingselectin antagonists and VLA-4 antagonists. These combination therapiescan be part of an immunomodulating regimens or a regimen for thetreatment or prevention of allo- or xenograft acute or chronicrejection, an inflammatory disorder, or an autoimmune disorders.

Multiple Sclerosis

Multiple sclerosis (MS) is a central nervous system disease that ischaracterized by inflammation and loss of myelin sheaths.

Patients having MS may be identified by criteria establishing adiagnosis of clinically definite MS as defined by the workshop on thediagnosis of MS (Poser et al., Ann. Neurol. 13:227, 1983). MS may alsobe diagnosed by evidence of two attacks and oligoclonal bands of IgG incerebrospinal fluid or by combination of an attack, clinical evidence oftwo lesions and oligoclonal band of IgG in cerebrospinal fluid. TheMcDonald criteria can also be used to diagnose MS. McDonald et al.(2001) Recommended diagnostic criteria for multiple sclerosis:guidelines from the International Panel on the Diagnosis of MultipleSclerosis, Ann Neurol 50:121-127. The McDonald criteria include the useof MRI evidence of CNS impairment over time to be used in diagnosis ofMS, in the absence of multiple clinical attacks.

Effective treatment of multiple sclerosis may be evaluated in severaldifferent ways. The following parameters can be used to gaugeeffectiveness of treatment. Two exemplary criteria include: EDSS(extended disability status scale), and appearance of exacerbations onMRI (magnetic resonance imaging). The EDSS is a means to grade clinicalimpairment due to MS (Kurtzke, Neurology 33:1444, 1983). Eightfunctional systems are evaluated for the type and severity of neurologicimpairment. Briefly, prior to treatment, patients are evaluated forimpairment in the following systems: pyramidal, cerebella, brainstem,sensory, bowel and bladder, visual, cerebral, and other. Follow-ups areconducted at defined intervals. The scale ranges from 0 (normal) to 10(death due to MS). A decrease of one full step can indicate an effectivetreatment (Kurtzke, Ann. Neurol. 36:573-79, 1994).

Exemplary symptoms associated with multiple sclerosis, which can betreated with the methods described herein, include: optic neuritis,diplopia, nystagmus, ocular dysmetria, internuclear ophthalmoplegia,movement and sound phosphenes, afferent pupillary defect, paresis,monoparesis, paraparesis, hemiparesis, quadraparesis, plegia,paraplegia, hemiplegia, tetraplegia, quadraplegia, spasticity,dysarthria, muscle atrophy, spasms, cramps, hypotonia, clonus,myoclonus, myokymia, restless leg syndrome, footdrop, dysfunctionalreflexes, paraesthesia, anaesthesia, neuralgia, neuropathic andneurogenic pain, l'hermitte's, proprioceptive dysfunction, trigeminalneuralgia, ataxia, intention tremor, dysmetria, vestibular ataxia,vertigo, speech ataxia, dystonia, dysdiadochokinesia, frequentmicturation, bladder spasticity, flaccid bladder, detrusor-sphincterdyssynergia, erectile dysfunction, anorgasmy, frigidity, constipation,fecal urgency, fecal incontinence, depression, cognitive dysfunction,dementia, mood swings, emotional lability, euphoria, bipolar syndrome,anxiety, aphasia, dysphasia, fatigue, uhthoffs symptom, gastroesophagealreflux, and sleeping disorders.

In addition to or prior to human studies, an animal model can be used toevaluate the efficacy of using the two agents. An exemplary animal modelfor multiple sclerosis is the experimental autoimmune encephalitis (EAE)mouse model, e.g., as described in (Tuohy et al. (J. Immunol. (1988)141: 1126-1130), Sobel et al. (J. Immunol. (1984) 132: 2393-2401), andTraugott (Cell Immunol. (1989) 119: 114-129). Mice can be administered afirst and second agent described herein prior to EAE induction. Then themice are evaluated for characteristic criteria to determine the efficacyof using the two agents in the model.

IBD

Inflammatory bowel diseases (IBD) include generally chronic, relapsingintestinal inflammation. IBD refers to two distinct disorders, Crohn'sdisease and ulcerative colitis (UC). The clinical symptoms of IBDinclude intermittent rectal bleeding, crampy abdominal pain, weight lossand diarrhea. A clinical index can also be used to monitor IBD such asthe Clinical Activity Index for Ulcerative Colitis. See also, Walmsleyet al. Gut. 1998 July; 43(1):29-32 and Jowett et al. (2003) Scand JGastroenterol. 38(2):164-71. An FcRn-binding antibody can be used toameliorate at least one symptom of IBD or to ameliorate a clinical indexof IBD.

Rheumatoid Arthritis

Rheumatoid arthritis is an autoimmune inflammatory disease that causespain, swelling, stiffness, and loss of function in the joints.Rheumatoid arthritis often presents in a symmetrical pattern. Thedisease can affect the wrist joints and the finger joints closest to thehand. It can also affect other parts of the body besides the joints. Inaddition, people with rheumatoid arthritis may have fatigue, occasionalfevers, and a general malaise. Positive factors for diagnosis ofrheumatoid arthritis include the “rheumatoid factor” blood antibody andcitrulline antibody. An FcRn-binding antibody can be useful in treating,preventing, or alleviating rheumatoid arthritis or one or more symptomsof rheumatoid arthritis.

Lupus

Systemic lupus erythematosus (SLE) is an autoimmune disorder that leadsto inflammation and damage to various body tissues. SLE can be mediatedby self-antibodies directed against its own DNA. Lupus can affect manyparts of the body, including the joints, skin, kidneys, heart, lungs,blood vessels, and brain. Although various symptoms may present, some ofthe most common include extreme fatigue, painful or swollen joints(arthritis), unexplained fever, skin rashes, and kidney problems.Exemplary symptoms of lupus include painful or swollen joints,unexplained fever, and extreme fatigue. A characteristic red skin rashmay appear across the nose and cheeks. Rashes may also occur on the faceand ears, upper arms, shoulders, chest, and hands. Other symptoms oflupus include chest pain, hair loss, anemia, mouth ulcers, and pale orpurple fingers and toes from cold and stress. Some people alsoexperience headaches, dizziness, depression, confusion, or seizures.Positive factors for SLE diagnosis include circulating anti-nuclearantibodies, anti-DNA antibodies, and anti-Sm antibodies. An FcRn-bindingantibody can be useful in treating, preventing, or alleviating SLE orone or more symptoms of SLE. Lupus, as used herein includes cutaneouslupus and lupus nephritits.

Immune Thromocytopenia (ITP)

ITP is a disease of increased peripheral platelet destruction, wherepatients develop antibodies that bind to specific platelet membraneproteins. The anti-platelet antibodies opsonize the platelets, leadingto destruction by macrophages. Attempts to treat ITP have generallyinvolved suppressing the immune system, which causes an increase inplatelet levels. An FcRn-binding antibody can be useful in treating,preventing, or alleviating ITP, or one or more symptoms thereof.

Ankylosing Spondylitis

Ankylosing spondylitis is an autoimmune disorder that not only affectsthe spine, but may also affect the hips, shoulders, and knees as thetendons and ligaments around the bones and joints become inflamed,resulting in pain and stiffness. Ankylo sing spondylitis tends to affectpeople in late adolescence or early adulthood. An FcRn-binding antibodycan be useful in treating, preventing, or alleviating ankylosingspondylitis, or one or more symptoms thereof.

Pemphigus

Pemphigus is an autoimmune disorder that affects mucous membranes andthe skin. The disorder is characterized by the generation ofauto-antibodies against desmoglein. Desmoglein is a protein in thefamily of cadherins and is involved with the formation of desmosomes,which join cells to one another. Pemphigus can be classified as one ofthree types: pemphigus vulgaris, the most common form of the disorder,wherein auto-antibodies target desmoglein 3. In pemphigus folicaeusauto-antibodies against desmoglein 1 are generated. The third type, andleast common disorder is paraneoplastic pemphigus, whereinautoantibodies target desmoplakins and which is associated with cancerssuch as lymphoma. The disorders are commonly diagnosed by adermatologist by the appearance of the skin and is conformed by thedetection of auto-antibodies against desmoglein. Methods of treatmentinclude the administration of steroids and/or the administration of aCD20 antibody such as Rituximab (Rituxan)

Cancer

“Cancer” as used herein refers to an uncontrolled growth of cells whichinterferes with the normal functioning of the bodily organs and systems.Cancers which migrate from their original location and seed vital organscan eventually lead to the death of the subject through the functionaldeterioration of the affected organs. Carcinomas are malignant cancersthat arise from epithelial cells and include adenocarcinoma and squamouscell carcinoma. Sarcomas are cancer of the connective or supportivetissue and include osteosarcoma, chondrosarcoma and gastrointestinalstromal tumor. Hematopoietic cancers, such as leukemia, are able tooutcompete the normal hematopoietic compartments in a subject, therebyleading to hematopoietic failure (in the form of anemia,thrombocytopenia and neutropenia) ultimately causing death. A person ofordinary skill in the art can classify a cancer as a sarcoma, carcinomaor hematopoietic cancer.

Cancer, as used herein, includes the following types of cancer, breastcancer, biliary tract cancer; bladder cancer; brain cancer includingglioblastomas and medulloblastomas; cervical cancer; choriocarcinoma;colon cancer; endometrial cancer; esophageal cancer; gastric cancer;hematological neoplasms including acute lymphocytic and myelogenousleukemia; T-cell acute lymphoblastic leukemia/lymphoma; hairy cellleukemia; chromic myelogenous leukemia, multiple myeloma;AIDS-associated leukemias and adult T-cell leukemia lymphoma;intraepithelial neoplasms including Bowen's disease and Paget's disease;liver cancer; lung cancer; lymphomas including Hodgkin's disease andlymphocytic lymphomas; neuroblastomas; oral cancer including squamouscell carcinoma; ovarian cancer including those arising from epithelialcells, stromal cells, germ cells and mesenchymal cells; pancreaticcancer; prostate cancer; rectal cancer; sarcomas includingleiomyosarcoma, rhabdomyosarcoma, liposarcoma, fibrosarcoma, andosteosarcoma; skin cancer including melanoma, Kaposi's sarcoma,basocellular cancer, and squamous cell cancer; testicular cancerincluding germinal tumors such as seminoma, non-seminoma (teratomas,choriocarcinomas), stromal tumors, and germ cell tumors; thyroid cancerincluding thyroid adenocarcinoma and medullar carcinoma; and renalcancer including adenocarcinoma and Wilms tumor. Other cancers will beknown to one of ordinary skill in the art.

Treatment of Fetuses

FcRn mediates the transport of maternal IgG across epithelial cellbarriers to fetus. The antibodies described herein can be used todeliver macromolecular drugs, e.g., antibiotics, and/or small moleculesto fetuses in utero. The fetus may be suffering from a condition ordisorder (e.g., an enteric infection or metabolic disorder) thatrequires treatment. The drug or molecule for treating the condition ordisorder can be conjugated to a FcRn binding antibody and administeredto a pregnant woman who has an in utero fetus that is in need oftreatment. The conjugated FcRn-binding antibody binds to FcRn and isthereby transported to the fetus via the placenta. The fetus receivesthe drug or molecule treatment.

Immunoadsorption

In some embodiments, the invention provides methods for the removal ofan unwanted therapeutic antibody from an individual. In someembodiments, the unwanted therapeutic antibody is an IgG antibody. Insome embodiments the unwanted therapeutic antibody is an anti-VLA4antibody such as Natalizumab (Tysabri, Biogen Idec/Elan), efalizumab(Raptiva, Genetech), bevacizumab (Avastin, Genentech) and Fc fusionproteins such as etanercept (Enbrel, Amgen/Wyeth). Natalizumabmonoclonal antibody therapy has been associated with ProgressiveMultifocal Leukoencephalopathy (PML). Depletion of the therapeuticantibody from the bloodstream and/or the rest of the body may alter theprogression of PML.

In some embodiments, the treatment methods presented herein may becombined with methods to remove or partially remove therapeuticantibodies from the bloodstream of a subject. In some embodiments, theanti-FcRn antibodies presented herein may be combined with a captureprotein that can bind a therapeutic antibody, the combinations resultingin an increased clearance of the therapeutic antibody from thebloodstream. In some embodiments, the method of removal or partialremoval of the therapeutic antibody from the bloodstream of a subject isplasma exchange (PLEX). In some embodiments, the anti-FcRn antibodiescan be administered to a subject undergoing plasma exchange. In someembodiments, the anti-FcRn antibodies can be used as an immunoadsorbantfor FcRn in the plasma exchange process.

In plasma exchange (also called apheresis or plasmapheresis) blood istaken from the body and plasma containing an unwanted agent, such ascholesterol or a therapeutic antibody, is removed from the blood by acell separator. Blood can be removed from the body in batches or it canbe removed in a continuous flow mode, with the latter allowing for thereintroduction of the processed blood into the body. The removed plasmacomprising the unwanted agent can be discarded and the patient canreceive donor plasma or saline with added proteins in return. In someembodiments, multiple rounds of plasma exchange may be needed to removethe unwanted agent from the blood or to lower the level of the unwantedagent in the blood to an acceptable level. In some embodiments the bloodis “filtered” and the unwanted agent removed, before returning the bloodto the patient. Methods of plasma exchange are known in the art and aredescribed, for example, in U.S. Pat. No. 6,960,178.

Plasma exchange has been shown to reduce therapeutic antibody levels inthe blood of a subject and the restoration of homeostasis (See e.g.,Khatri et al; 2009; Neurology 72:402-409).

An IgG based therapeutic antibody (such as natalizumab) can be removedfrom blood, plasma or serum by contacting the blood with the captureprotein Staphylococcal protein A, which will bind the Fc region of IgGand remove the IgG antibody from the bloodstream.

Other capture proteins can be used for different isotype antibodies. Insome embodiments, the anti-FcRn antibodies can be used as a captureprotein in the plasma exchange process, resulting in the removal of FcRnfrom the bloodstream, thereby increasing the amount of “free”therapeutic antibody. The resulting “free” therapeutic antibody willhave a shorter half-life than antibody present prior to treatment and/orcan be removed from the blood more readily with a different captureprotein (such as protein A). In some embodiments, the anti-FcRnantibodies are administered to a patient during or before plasmaexchange. In some embodiments, the anti-FcRn antibodies can beimmobilized and used in a column, resulting in the binding of FcRn. Insome embodiments, the blood of a patient that contains a therapeuticantibody is contacted both with immobilized anti-FcRn antibody andimmobilized protein A.

In some embodiments the anti-FcRn antibodies presented herein can beused in “rescue” therapy for therapeutic antibodies that have beenadministered and have shown an adverse effect. In some embodiments, ananti-FcRn antibody can be used as an alternative for plasma exchange.The administration of an anti-FcRn can accomplish therapeutic antibodydepletion without the risks associated with plasmapheresis and plasmaexchange such as vascular access, citrate therapy and donor plasmasourcing.

Human Leukocyte Antigens

Human leukocyte antigens (HLA) present peptides and antigens on theoutside of the cell, which are subsequently recognized by T-cells, whichin their turn can activate B-cells. The panel of HLA genes available isunique for each person. Any cell displaying an HLA that is “non-self”will result in the induction of an immune response. In general, the moredifferent the “non-self” HLA from the self HLA, the stronger the immuneresponse. For instance, in the case of organ transplants, subjects withsimilar HLA genes are preferred to minimize the immune response.Donor-specific HLA antibodies have been found to be associated withgraft failure in kidney, heart, lung and liver transplantation.

In some embodiments, the invention provides methods for the decreasingthe level of “non-self” HLA antibodies in an individual. Decreasing thelevel of “non-self” HLA antibodies can result in the suppression of animmune response, e.g., during organ transplantation. In some embodimentsa person that will be undergoing organ transplation is administered ananti-FcRn antibody. In some embodiments a person that is undergoingorgan transplation is administered an anti-FcRn antibody. In someembodiments a person that has received an organ transplation isadministered an anti-FcRn antibody. Assays for measuring the levels ofHLA antibodies are well-known in the art.

Diagnostic Uses

Antibodies that bind to FcRn and identified by the method describedherein and/or detailed herein have in vitro and in vivo diagnosticutilities.

In one aspect, the disclosure provides a diagnostic method for detectingthe presence of an FcRn, in vitro or in vivo (e.g., in vivo imaging in asubject). The method can include localizing FcRn to a subcellularlocation, e.g., the endosome. The method can include: (i) contacting asample with FcRn-binding antibody; and (ii) detecting formation of acomplex between the FcRn-binding antibody and the sample. The method canalso include contacting a reference sample (e.g., a control sample) withthe antibody, and determining the extent of formation of the complexbetween the antibody and the sample relative to the same for thereference sample. A change, e.g., a statistically significant change, inthe formation of the complex in the sample or subject relative to thecontrol sample or subject can be indicative of the presence of FcRn inthe sample.

Another exemplary method includes: (i) administering the FcRn-bindingantibody to a subject; and (iii) detecting formation of a complexbetween the FcRn-binding antibody and the subject. The detecting caninclude determining location or time of formation of the complex.

The FcRn-binding antibody can be directly or indirectly labeled with adetectable substance to facilitate detection of the bound or unboundantibody. Suitable detectable substances include various enzymes,prosthetic groups, fluorescent materials, luminescent materials andradioactive materials.

Complex formation between the FcRn-binding antibody and FcRn can bedetected by measuring or visualizing either the antibody bound to theFcRn or unbound antibody. Conventional detection assays can be used,e.g., an enzyme-linked immunosorbent assays (ELISA), a radioimmunoassay(RIA) or tissue immunohistochemistry. Further to labeling theFcRn-binding antibody, the presence of FcRn can be assayed in a sampleby a competition immunoassay utilizing standards labeled with adetectable substance and an unlabeled FcRn-binding antibody. In oneexample of this assay, the biological sample, the labeled standards, andthe FcRn-binding antibody are combined and the amount of labeledstandard bound to the unlabeled antibody is determined. The amount ofFcRn in the sample is inversely proportional to the amount of labeledstandard bound to the FcRn-binding antibody.

Fluorophore and chromophore labeled antibodies can be prepared. Becauseantibodies and other proteins absorb light having wavelengths up toabout 310 nm, the fluorescent moieties should be selected to havesubstantial absorption at wavelengths above 310 nm and preferably above400 nm. A variety of suitable fluorescers and chromophores are describedby Stryer, 1968, Science 162:526 and Brand, L. et al., 1972, Annu. Rev.Biochem. 41:843 868. The antibodies can be labeled with fluorescentchromophore groups by conventional procedures such as those disclosed inU.S. Pat. Nos. 3,940,475, 4,289,747, and 4,376,110. One group offluorescers having a number of the desirable properties described aboveis the xanthene dyes, which include the fluoresceins and rhodamines.Another group of fluorescent compounds are the naphthylamines Oncelabeled with a fluorophore or chromophore, the antibody can be used todetect the presence or localization of the FcRn in a sample, e.g., usingfluorescent microscopy (such as confocal or deconvolution microscopy).

Histological Analysis.

Immunohistochemistry can be performed using the antibodies describedherein. For example, the antibody can be synthesized with a label (suchas a purification or epitope tag), or can be detectably labeled, e.g.,by conjugating a label or label-binding group. For example, a chelatorcan be attached to the antibody. The antibody is then contacted to ahistological preparation, e.g., a fixed section of tissue that is on amicroscope slide. After an incubation for binding, the preparation iswashed to remove unbound antibody. The preparation is then analyzed,e.g., using microscopy, to identify if the antibody bound to thepreparation.

Of course, the antibody can be unlabeled at the time of binding. Afterbinding and washing, the antibody is labeled in order to render itdetectable.

Protein Arrays.

The FcRn-binding antibody can also be immobilized on a protein array.The protein array can be used as a diagnostic tool, e.g., to screenmedical samples (such as isolated cells, blood, sera, biopsies, and thelike). Of course, the protein array can also include other ligands,e.g., that bind to FcRn or to other target molecules.

Methods of producing polypeptide arrays are described, e.g., in De Wildtet al., 2000, Nat. Biotechnol. 18:989-994; Lueking et al., 1999, Anal.Biochem. 270:103-111; Ge, 2000, Nucleic Acids Res. 28, e3, I-VII;MacBeath and Schreiber, 2000, Science 289:1760-1763; WO 01/40803 and WO99/51773A1. Polypeptides for the array can be spotted at high speed,e.g., using commercially available robotic apparati, e.g., from GeneticMicroSystems or BioRobotics. The array substrate can be, for example,nitrocellulose, plastic, glass, e.g., surface-modified glass. The arraycan also include a porous matrix, e.g., acrylamide, agarose, or anotherpolymer.

For example, the array can be an array of antibodies, e.g., as describedin De Wildt, supra. Cells that produce the antibodies can be grown on afilter in an arrayed format. Antibody production is induced, and theexpressed polypeptides are immobilized to the filter at the location ofthe cell. An antibody array can be contacted with a labeled target todetermine the extent of binding of the target to each immobilizedantibody. Information about the extent of binding at each address of thearray can be stored as a profile, e.g., in a computer database. Theantibody array can be produced in replicates and used to compare bindingprofiles, e.g., of a target and a non-target.

FACS (Fluorescence Activated Cell Sorting).

The FcRn-binding antibody can be used to label cells, e.g., cells in asample (e.g., a patient sample). The antibody is also attached (orattachable) to a fluorescent compound. The cells can then be sortedusing fluorescence activated cell sorter (e.g., using a sorter availablefrom Becton Dickinson Immunocytometry Systems, San Jose Calif.; see alsoU.S. Pat. Nos. 5,627,037; 5,030,002; and 5,137,809). As cells passthrough the sorter, a laser beam excites the fluorescent compound whilea detector counts cells that pass through and determines whether afluorescent compound is attached to the cell by detecting fluorescence.The amount of label bound to each cell can be quantified and analyzed tocharacterize the sample.

The sorter can also deflect the cell and separate cells bound by theantibody from those cells not bound by the antibody. The separated cellscan be cultured and/or characterized.

In Vivo Imaging.

Also featured is a method for detecting the presence of aFcRn-expressing tissues in vivo. The method includes (i) administeringto a subject (e.g., a patient having an autoimmune disorder) ananti-FcRn antibody, conjugated to a detectable marker; (ii) exposing thesubject to a means for detecting said detectable marker to theFcRn-expressing tissues or cells. For example, the subject is imaged,e.g., by NMR or other tomographic means.

Examples of labels useful for diagnostic imaging include radiolabelssuch as ¹³¹I, ¹¹¹In, ¹²³I, ⁹⁹mTc, ³²P, ¹²⁵I, ³H, ¹⁴C, and ¹⁸⁸Rh,fluorescent labels such as fluorescein and rhodamine, nuclear magneticresonance active labels, positron emitting isotopes detectable by apositron emission tomography (“PET”) scanner, chemiluminescers such asluciferin, and enzymatic markers such as peroxidase or phosphatase.Short range radiation emitters, such as isotopes detectable by shortrange detector probes can also be employed. The antibody can be labeledwith such reagents using known techniques. For example, see Wensel andMeares, 1983, Radioimmunoimaging and Radioimmunotherapy, Elsevier, NewYork for techniques relating to the radiolabeling of antibodies and D.Colcher et al., 1986, Meth. Enzymol. 121: 802 816.

A radiolabeled antibody can also be used for in vitro diagnostic tests.The specific activity of a isotopically-labeled antibody depends uponthe half life, the isotopic purity of the radioactive label, and how thelabel is incorporated into the antibody.

Procedures for labeling polypeptides with the radioactive isotopes (suchas ¹⁴C, ³H, ³⁵S, ¹²⁵I, 3²P ¹³¹I) are generally known. For example,tritium labeling procedures are described in U.S. Pat. No. 4,302,438.Iodinating, tritium labeling, and ³⁵S labeling procedures, e.g., asadapted for murine monoclonal antibodies, are described, e.g., byGoding, J. W. (Monoclonal antibodies: principles and practice:production and application of monoclonal antibodies in cell biology,biochemistry, and immunology 2nd ed. London; Orlando: Academic Press,1986. pp 124 126) and the references cited therein. Other procedures foriodinating polypeptides, such as antibodies, are described by Hunter andGreenwood, 1962, Nature 144:945, David et al., 1974, Biochemistry13:1014 1021, and U.S. Pat. Nos. 3,867,517 and 4,376,110. Radiolabelingelements which are useful in imaging include ¹²³I, ¹³¹I, ¹¹¹In, and⁹⁹mTc, for example. Procedures for iodinating antibodies are describedby Greenwood, F. et al., 1963, Biochem. J. 89:114 123; Marchalonis, J.,1969, Biochem. J. 113:299 305; and Morrison, M. et al., 1971,Immunochemistry 289 297. Procedures for ^(99m)Tc labeling are describedby Rhodes, B. et al. in Burchiel, S. et al. (eds.), Tumor Imaging: TheRadioimmunochemical Detection of Cancer, New York: Masson 111 123 (1982)and the references cited therein. Procedures suitable for ¹¹¹In labelingantibodies are described by Hnatowich, D. J. et al., 1983, J. Immunol.Methods, 65:147 157, Hnatowich, D. et al., 1984, J. Applied Radiation,35:554 557, and Buckley, R. G. et al., 1984, F.E.B.S. 166:202 204.

In the case of a radiolabeled antibody, the antibody is administered tothe patient, is localized to cells bearing the antigen with which theantibody reacts, and is detected or “imaged” in vivo using knowntechniques such as radionuclear scanning using e.g., a gamma camera oremission tomography. See e.g., A. R. Bradwell et al., “Developments inAntibody Imaging”, Monoclonal Antibodies for Cancer Detection andTherapy, R. W. Baldwin et al., (eds.), pp 65 85 (Academic Press 1985).Alternatively, a positron emission transaxial tomography scanner, suchas designated Pet VI located at Brookhaven National Laboratory, can beused where the radiolabel emits positrons (e.g., ¹¹C, ¹⁸F, ¹⁵O, and¹³N).

MRI Contrast Agents.

Magnetic Resonance Imaging (MRI) uses NMR to visualize internal featuresof living subject, and is useful for prognosis, diagnosis, treatment,and surgery. MRI can be used without radioactive tracer compounds forobvious benefit. Some MRI techniques are summarized in EP-A-0 502 814.Generally, the differences related to relaxation time constants T1 andT2 of water protons in different environments is used to generate animage. However, these differences can be insufficient to provide sharphigh resolution images.

The differences in these relaxation time constants can be enhanced bycontrast agents. Examples of such contrast agents include a number ofmagnetic agents paramagnetic agents (which primarily alter T1) andferromagnetic or superparamagnetic (which primarily alter T2 response).Chelates (e.g., EDTA, DTPA and NTA chelates) can be used to attach (andreduce toxicity) of some paramagnetic substances (e.g., Fe⁺³, Mn⁺²,Gd⁺³). Other agents can be in the form of particles, e.g., less than 10mm to about 10 nM in diameter). Particles can have ferromagnetic,antiferromagnetic, or superparamagnetic properties. Particles caninclude, e.g., magnetite (Fe₃O₄), .gamma.-Fe₂O₃, ferrites, and othermagnetic mineral compounds of transition elements. Magnetic particlesmay include: one or more magnetic crystals with and without nonmagneticmaterial. The nonmagnetic material can include synthetic or naturalpolymers (such as sepharose, dextran, dextrin, starch and the like.

The FcRn-binding antibody can also be labeled with an indicating groupcontaining of the NMR active ¹⁹F atom, or a plurality of such atomsinasmuch as (i) substantially all of naturally abundant fluorine atomsare the ¹⁹F isotope and, thus, substantially all fluorine containingcompounds are NMR active; (ii) many chemically active polyfluorinatedcompounds such as trifluoracetic anhydride are commercially available atrelatively low cost; and (iii) many fluorinated compounds have beenfound medically acceptable for use in humans such as the perfluorinatedpolyethers utilized to carry oxygen as hemoglobin replacements. Afterpermitting such time for incubation, a whole body MRI is carried outusing an apparatus such as one of those described by Pykett, 1982, Sci.Am. 246:78 88 to locate and image tissues expressing FcRn.

The disclosure also features kits comprising an antibody that binds toFcRn and instructions for diagnostic use, e.g., the use of theFcRn-binding antibody or antigen-binding fragment thereof, to detectFcRn, in vitro, e.g., in a sample, e.g., a biopsy or cells from apatient having an autoimmune disorder, or in vivo, e.g., by imaging asubject. The kit can further contain a least one additional reagent,such as a label or additional diagnostic agent. For in vivo use theantibody can be formulated as a pharmaceutical composition.

The present invention is further illustrated by the following Examples,which in no way should be construed as further limiting. The entirecontents of all of the references (including literature references,issued patents, published patent applications, and co-pending patentapplications) cited throughout this application are hereby expresslyincorporated by reference, in particular for the teaching that isreferenced hereinabove.

EXAMPLES Example 1 Cloning FcRn, FcRn-GPI And β₂M

The full length FcRn cDNA construct used for these Examples wasoriginally constructed in the Simister lab (Brandeis University, WalthamMass.) using pcDNA6 (Invitrogen, Carlsbad, Calif.) as the plasmid vector(FcRn:pcDNA6). The Human β2m cDNA construct used for these Examples wasoriginally constructed in the Blumberg lab (Harvard Medical School,Boston, Mass.) using pcDNA3 (Invitrogen) as the plasmid vector(β2M:pcDNA3).

Plasmids were transfected into One Shot TOP10 chemically competent E.coli (Invitrogen, Carlsbad, Calif.) according to the manufacturer'sinstruction. A single colony was picked from each of the transformedplates, inoculated into 500-1000 ml of LB medium and cultured overnightin a shaker. Plasmid DNA was purified from these cultures with Maxi Prepkit (Qiagen, Valencia, Calif.). The pcDNA6-Full length hFcRn plasmidconstruct was digested with Nhe1 and Xba1. The pcDNA3.1-β2M plasmidconstruct was digested with Hind III and Xba 1. The pcDNA6-hFcRn-GPIplasmid construct was digested with Nhe1 and Xba 1. The digestedproducts were resolved on a 1% agarose gel to verify the size of theinsert was correct. The correct size for full-length FcRn and GPI-FcRnwere about 1 kb in length. Human β2M was about 0.4 kb in length. Theplasmid DNA (4 mg/ml in ethanol) was diluted to 2 mg/ml in sterile DPBS(Invitrogen, Carlsbad, Calif.) before intra-muscular injection.

Example 2 Immunization of Mice with FcRn-Encoding Plasmid DNA

Balb/c mice were treated with 100 μl of 10 mM cardiotoxin (Calbiochem,San Diego) 5 days before plasmid DNA injection. Cardiotoxin treatmentwas used to provoke an inflammatory response and to recruit antigenpresenting cells (e.g., dendritic cells) to the injected area, therebyimproving antigen presentation when the protein encoded by the plasmidwas expressed.

100 μg of full-length or GPI-hFcRn plasmid construct resuspended in 50μl of PBS were injected into the anterior tibialis muscle of the mice.Mice immunized with the combination of hFcRn and β2M received a dose of50 μg of hFcRn plasmid in 25 μl PBS and 50 μg of β2M plasmid in 25 μlPBS. All intra-muscular injections were performed under systemicanesthesia with pentobarbital (50 mg/kg, intraperitoneally) or ketamine(100 mg/kg)/Xylazine (10 mg/kg). Animals were boosted with additionalinjections of hFcRn plasmid DNA at 21 and 42 days after the firstimmunization using the same dose and volume as used for the firstinjection.

Mice were also boosted with the soluble form of recombinant hFcRn(shFcRn, 100 μg/mouse, intraperitoneally) on day 76 after the initialimmunization. Next, 30 to 50 μl of sera was obtained by tail veinbleeding at 56 and 94 days after the initial immunization. The sera asthen tested for antibody titers as described below in Example 3. Inaddition, mouse number 182 was given an intra-venous (IV) boost withrecombinant shFcRn (50 μg/mouse) on days 129, 130 and 131 before fusion.On day 132, spleen cells from mouse number 182 were fused with NS-1 orSP2/0 myeloma cells (ATCC, Manassas, Va.) as described below in Example4. About 35 anti-human FcRn specific mAB hybridoma lines were generatedfrom this fusion.

Mouse number 187 was further boosted IV with 50 μg of recombinant shFcRnon days 276, 277, and 278 after the initial immunization. On day 279,spleen cells from 187 were fused with SP2/0 myeloma cells as describedbelow in Example 4. 10% of the resulting fusions were plated in eleven96 well plates. The remaining 90% of the fusions were stored in liquidnitrogen. From the fusions plated, 35 lines that secrete mAB recognizinghFcRn were generated. The immunization protocol is summarized in Table2.

TABLE 2 IMMUNIZATION PROTOCOL Day Day Day Day No. of 129-131 132 276-278279 Vaccination mice Day 5 Day 0 Day 21 Day 42 Day 56 Day 76 Day 94 #182#182 #187 #187 Human 5 Cardio- Immu- Boost Boost 1^(st) Boost IP 2^(nd)Daily Fusion FL-FcRn- toxin nization Serum with Serum boost DNAtreatment test sHFcRn test with shFcRn IV Human 5 Cardio- Immu- BoostBoost Serum Boost IP Serum Daily Fusion FL-FcRn toxin nization test withtest boost DNA + treatment sHFcRn with Human shFcRn beta 2M IV DNA Human5 Cardio- Immu- Boost Boost Serum Boost IP Serum GPI-FcRn toxin nizationtest with test DNA treatment sHFcRn Human 5 Cardio- Immu- Boost BoostSerum Boost IP Serum GPI toxin nization test with test FcRn + treatmentsHFcRn Human beta 2M DNA No 5 Cardio- Serum Serum DNA toxin test testtreatment

Example 3 Antibody Titer in Mouse Serum

Anti-hFcRn and anti β₂M titer in mouse serum was measured by ELISA.ELISA plates were coated with 2 μg/ml of soluble hFcRn or hβ₂M (Sigma,St. Louis, Mo.) in ELISA coating buffer (Sigma, St. Louis, Mo.). Plateswere incubated at 37° C. for 1 hour. The plates were washed twice withPBS+0.05% Tween (PBST). The plates were blocked with 1% fish gelatin inPBS for 1 hour at 37° C. The plates were washed twice with PBST.Serially diluted mouse serum (in PBS) was added (100 μl/well) andincubated for 2 hours at 37° C. The plates were washed 5 times withPBST. Goat anti-mouse IgG-HRP (Pierce, Rockford, Ill.) at 1 to 10,000dilution was added to the plates and incubated for 1 hour at roomtemperature. The plates were washed 5 times with PBST.Tetramethylbenzidine (TMB) solution (KPL, Gaithersburg, Md.) was addedto the plates for color development. The substrate reaction was stoppedafter approximately 5 minutes when appropriate color developed. Theplates were read at 450 nM in a microplate reader (Bio-rad, Hercules,Calif.). Serum was tested in all mice at day 56 (FIG. 1). Those micewith serum reactive with hFcRn were tested again on day 94 and the serumtiters are shown in FIG. 2.

Example 4 Hybridoma Fusions

Mouse 182 and mouse 187 were selected for making hybridoma fusions. Thespleens of both mice were removed and single cell suspensions of spleencells were prepared by teasing the spleens apart followed by repeatedpipetting with 10 ml of DMEM media (Invitrogen, Carlsbad, Calif.). Thespleen cells were centrifuged at 500 g for 5 minutes. Red blood cellswere lysed by resuspending the spleen cells in 2 ml ACK lysis buffer(8.29 g NH₄Cl, 1 g KHCO₃, 37.2 mg Na₂EDTA, H₂O to a final volume of 1liter, pH 7.2-7.4). The cells were incubated on ice for 5 minutes. ACKbuffer treated cells were washed three times with DMEM. The total numberof spleen cells obtained from mouse 182 was 216×10⁶. One half of thecells was fused with 70×10⁶ SP2/0 myeloma cells and the other half wasfused with 27×10⁶ NS-1 cells.

The #182 fusion was carried out according to the method described inCurrent Protocol of Immunology Unit 2.5, Wayne M. Yokoyama, Publisher:John Wiley and Son Inc. Electronic version. SP2/0 fused cells werediluted in 314 ml HAT medium and seeded onto 16.5 plates (96 well plate,0.2 ml/well). NS-1 fused cells were diluted in 216 ml HAT medium andseeded onto 11 plates (96 well plate, 0.2 ml/well).

In the #187 fusion, 2×108 spleen cells were fused with 8×107 SP2/0myeloma cells using a protocol from “Monoclonal Antibodies” edited by J.H. Peters and H. Baumgarten, published by Springer-Verlag, 1992, Page149-156. New York.

On days 2, 3, 4, 5, 7, 9 after the fusion, half of the HAT medium wasreplaced with fresh HAT medium. One to two weeks after the fusion,hybidoma cells from positive wells (determined by clear growth under themicroscope and by naked eye inspection) were transferred to 24 wellculture plates. Within 2 weeks after the fusion, hybridoma cells werecultured in HAT media containing complete medium. On day 16, cells weretransferred to CDMEM without HAT.

When the medium turned slightly yellow, an aliquot of supernatant washarvested and screened for anti-hFcRn activity by ELISA as described inExample 3. A total of 384 hybridoma lines from SP2/0-#182 spleen cellfusion were screened. A total of 60 hybridoma lines from NS-1-#182spleen cell fusion were screened. Supernatants from 31 lines of SP2/0fusion tested positive by ELISA for anti-hFcRn reactivity. Supernatantsfrom 8 hybridoma lines of NS-1 fusion tested positive by ELISA foranti-hFcRn reactivity. A total of 16 hybridoma lines from #182 fusionwere cloned by limiting dilution and 3 subclones from each line wereselected for further characterization.

Example 5 Hybridoma Cloning

Hybridoma cloning media was prepared as follows: 12.5 ml hepes buffersolution (100×/1M) (Invitrogen, Carlsbad, Calif.), 5 ml sodium pyruvate(100×/100 mM) (Invitrogen, Carlsbad, Calif.), 5 mlpenicillin/streptomycin (100×/10,000 units) (Invitrogen, Carlsbad,Calif.), 5 ml non-essential amino acids (100×/100 mM) (Invitrogen,Carlsbad, Calif.), 5 ml L-glutamine (100×/200 mM) (Invitrogen, Carlsbad,Calif.), 0.5 ml 2-mercaptoethanol (1000×/5.5×10⁻² M) (Invitrogen,Carlsbad, Calif.), 100 ml FBS (prescreened for hybridoma growth)(Cambrex, East Rutherford, N.J.), and 50 ml of hybridoma cloning factor(ICN, Irvine, Calif.) were added to 317 ml high glucose DMEM(Invitrogen, Carlsbad, Calif.). The media was filtered through a 0.22 μmfilter and stored at 4° C.

Two days before cloning, the cDMEM culture media was replaced withhybridoma cloning media. On the day of cloning, the cells were washedonce in DMEM and the cells were counted. The cells were resuspended incloning medium at a concentration varied from 1×10⁵-1×10⁶/ml. 3000, 300or 100 cells were transferred to 20 ml cloning medium to makeconcentration of 150 cells/ml, 15 cells/ml or 3 cells/ml. The cells werethen transferred to 3 individual plates (one for each cellconcentration) of a 96 well plate. Each well has final volume of 0.2 ml.The plates were incubated at 37° C., 10% CO₂ for 1-2 weeks at whichpoint positive wells were counted. 20 30 clones were selected fromplates with the least positive wells and expanded into 24 well plates.The supernatants were tested by anti-FcRn ELISA as described in Example3 for reactivity to soluble FcRn.

Example 6 Cell Competition Assay Using FcRn Specific mAB Supernatants

A. Labeling of Synagis® with Alexa-Fluor-488

Synagis® (humanized IgG1, Medlmmune, Gaithersburg, Md.) was labeled withthe Alexa Fluor 488 Protein Labeling Kit (Molecular Probes/Invitrogen,Carlsbad, Calif.) according to the manufacturer's suggested protocol.Briefly, 50 μl of 1 M sodium bicarbonate, pH 9.0 was added to 500 μl ofa 2 mg/ml solution of IgG in PBS. This protein solution was then addedto the Alexa Fluor 488 succinimidyl ester (dry powder) and incubated atroom temperature for 1 hour. The protein was purified by size-exclusionchromatography using the kit component column (Bio-Rad BioGel P-30 Finesize exclusion purification resin). The sample was loaded onto thecolumn and eluted with PBS. The first colored band contained the labeledprotein. The degree of labeling was determined by measuring theabsorbance of the eluted IgG at A280 and A494. The protein molarconcentration was determined using the formula:

$(M) = \frac{\left\lbrack {A_{280} - {\left( {A_{194} \times 0.11} \right) \times {dilution}\mspace{14mu} {factor}}} \right\rbrack}{203,00}$

In addition, the formula used to derive the moles of dye per mole ofprotein was:

$(M) = \frac{A_{494} \times {dilution}\mspace{14mu} {factor}}{71,000 \times {protein}\mspace{14mu} {concentration}}$

Typically, 4 to 7 moles of Alexa-Fluor 488 were incorporated per mole ofIgG. B. Cell

B. Cell Competition Assay with FcRn Specific Supernatants

293 C11 cells expressing hFcRn and human (3₂M were used to test FcRn mABsupernatants in a competition assay with a fluorescently labeled IgG1.300,000 293 C11 cells were washed in PBS and pelleted in a table topmicro-centrifuge at 2500 RPM for 5 minutes. The pelleted cells wereresuspended in 100-200 μl of supernatant from clones producing FcRnspecific mABs and incubated on ice for 60-90 minutes. The cells werewashed twice with binding buffer (PBS pH 6.0 10 mM EDTA). The cells wereresuspended in 100 μl of binding buffer. Alexa fluor 488 (MolecularProbes, Eugene, Oreg.) labeled hIgG1 was prepared using a kit (MolecularProbes, Eugene, Oreg.) according to the manufacturer's instructions andadded to each tube (100 nM in 0.6-1.5 μl). The cells were incubated for40 minutes on ice. The cells were washed once in binding buffer andanalyzed by fluorescent activated cell sorter (FACS) using EXPO.32software (Beckman Coulter, Inc., Miami, Fla.). The results are presentedas total mean fluorescence intensity (TMFI).

FIGS. 3A and 3B depict results from the 182 fusions. If the TMFI of thecontrol tube (Alexa Fluor 488 alone and without competitor) is higherthan the TMFI of the tube containing competitor (mAB sup), theinhibition rate was calculated as follows:

TMFI of control tube−TMFI of competitor containing tube/TMFI of controltube.

If TMFI of the control tube is lower than the TMFI of competitorcontaining tube, there is enhancement of hIgG1 binding to FcRnexpressing cells. The enhancement was calculated as follows:

TMFI of competitor containing tube−TMFI of control tube/TMFI of controltube.

FIGS. 4A and 4B depict results from the 187 fusion. TMFI was calculatedas fraction of cells in the gated region multiplied by mean fluorescencein the region. The results of one experiment indicated 11 of thesupernatants tested inhibited IgG1 labeled with Alexa fluor 188 bindingto 293C11 cells, while 4 of the supernatants enhanced binding of IgG1labeled with Alexa fluor 188 binding to 293C11 (FIG. 4A). The results ofa second experiment indicated that 3 supernatants inhibited IgG1 bindingto 293 C11 cells, while 5 supernatants enhanced binding (FIG. 4B).

Example 7 Cell Competition Assay Using Purified FcRn Specific mABs

293 C11 cells expressing hFcRn and human (3₂M were used to test FcRn mABsupernatants in a competition assay with a fluorescently labeled IgG1.The cells were washed once with binding buffer (PBS pH 6.0, 10 mM EDTA)and pelleted at 1800 RPM, 4° C. in a table top centrifuge. The cellswere aliquoted into micro-centrifuge tubes (1-3×10⁵/vial/ml bindingbuffer). The cells were pelleted in a micro-centrifuge at 2500 RPM forfive minutes. The supernatant was aspirated and the cell pellet wasresuspended in 100 (0.1.1 of binding buffer. Purified FcRn specific mABswere added at various concentrations. Alexa fluor 488 (Molecular Probes,Eugene, Oreg.) labeled IgG was added at a concentration of 100 nM (finalconcentration) to each tube. The samples were incubated at 4° C. for 40minutes. The samples were washed once with binding buffer andresuspended in binding buffer for FACS analysis (Beckman Coulter, Inc.,Miami, Fla.). Before sample analysis the FACS was equilibrated withbinding buffer. The results are presented as total mean fluorescenceintensity (TMFI). TMFI was calculated as percentage of cells in thegated region×mean fluorescence in the region. The results indicated themAB 3B3.11, mAB 4B4.12, mAB 31.1 and mAB 4.13 inhibited IgG1 binding to293 C11 cells significantly (FIGS. 5A and 5B).

Example 8 Cell Surface Staining for FcRn Using Monoclonal Antibodies

Surface expression of FcRn using mABs was detected by FACS. Ratfibroblasts (expressing rat FcRn/rat β₂M) 293 C11 cells (expressinghFcRn/human β₂M), 3T3 FcRn cells (expressing murine FcRn/murine β₂M) andCOS cells transfected with plasmid pcDNA6 encoding monkey FcRN/β₂M werestudied. A micro-centrifuge was used to pellet 1-3×10⁵ of each celltype. The supernatant was removed and the cells were resuspended in 1 μgof mAB labeled with Alexa 488 (Molecular Probes, Eugene, Oreg.) in afinal volume of 100 μl of PBS/1% bovine serum albumin (pH 7.4). PurifiedmABs specific to FcRn were previously labeled with Alexa Fluor 488(Molecular Probes, Eugene, Oreg.) using the Alexa Fluor Protein LabelingKit (Molecular Probes, Eugene, Oreg.) according to the manufacturersinstructions. The cells were incubated on ice for 45 minutes and thenwashed once with PBS/1% bovine serum albumin (pH 7.2). FACS analysis wasperformed using a Beckman Coulter, Inc. FACS (Beckman Coulter, Inc.,Miami Fla.). The results are presented in FIGS. 6, 7, and 8. FIG. 6shows that mABs 3B3.11, 31.1, 4.13, 4B.12 and 15B6.1 all recognizedhFcRn expressed on the cell surface of 293 C11 cells. FIG. 7 shows thatmABs 4.13 and 4B4.12 also recognized rat FcRn expressed on the surfaceof cells expressing rat FcRn while mABs 3B3.11 and 31.1 did not crossreact with rat FcRn. FIG. 8 shows that mABs 3B3.11, 4B4.12 and 4.13recognized murine FcRn expressed on the cell surface of mouse 3T3 cells,while 15B6.1 and 31.1 did not cross react.

Example 9 Sub-Cloning of Various Hybridoma Cell Lines

Hybridomas from mouse 187 were selected for sub-cloning. Hybridomas 6A4,6A1, 5A4, 7D2, 4B4, 3C5, 3B3, 10B4, 1C1, and 11A5 were selected forsub-cloning. Sub-cloning was performed by limiting dilution. 3B5 clonessecrets anti-hβ2 M antibody. Between 20 and 30 sub-clones were grown andthe supernatants from the cultures were tested by ELISA as described inExample 3. Cultures from 2-10 positive clones were expanded into T150flasks (4 flasks per clone). A total of 350-400 ml of supernatant washarvested for mAB purification. The mAB yield from each clone rangedfrom 3-20 mg. The purified mABs were tested for FcRn blocking using the293 C11 competition assay as described in Example 7. The mABs weretitrated 2-fold from 1000 nM to 16 nM for the competition assay. Asummary of the results obtained for the 187 sub-clones and the 182clones is presented in Table 3.

TABLE 3 Characterization of mABs from #182 fusion and #187 fusionBlocking test Blocking ELISA (sup) % of IgG (purified) Clones (shFcRn)inhibition Isotyping % Inhibition #182 fusions 4.13 + >50 IgG1 90 15B6.1++ >50 IgG2a 14C5.3 + >40 IgG2a 31.1 + >40 IgG1 93 3C6.2 + >35 IgG2a 74#187 fusion 3B3.11 ++ >60 IgG1 92 3B3.16 ++ >60 IgG1 73 3B3.21 ++++ >60IgG1 84 3B3.35 ++ >60 IgG1 86 6A4.1 + >40 IgG1 42 6A4.4 + >40 IgG1 526A4.16 + >40 IgG1 65 6A4.17 + >40 IgG1 42 6A1.12 + 21 IgG1 IgG2a 356A1.13 + 25 IgG2a 39 6A1.29 + 33 IgG2a 81 3B5.2(@β2m) +++ 71 IgG2a 903B5.4(@β2m) +++ 79 IgG2a 52 3B5.5(@β2m) +++ 63 IgG2a 3B5.9(@β2m) +++ 71IgG2a 80 7D2.13 + 49 IgG1 IgG2a 11 7D2.21 ++ 43 7D2.22 + 49 IgG1 IgG2a43 7D2.27 + 46 IgG1 52 5A4.9 + 57 5A4.10 + 49 IgG1 63 5A4.25 + 54 IgG131 5A4.27 + 51 39 5A4.38 + 43 15 5A4.39 + 49 20 5A4.40 + 53 30 5A4.41 +66 35 5A4.42 + 72 4B4.1 ++ 70 IgG2a 4B4.2 ++ 66 IgG2a 69 4B4.12 ++ 70IgG2a 71 4B4.13 ++ 66 IgG2a 60 3C5.10 + 30 3C5.11 + 40 3C5.14 + 403C5.16 + 33 10B4.5 +++ 23 54 10B4.9 ++ 23 31 1C1.7 +++ 32 IgG1 23 1C1.22+++ 27 IgG1 61 1C1.23 +++ 32 IgG1 27 1C1.25 ++ 32 IgG1 38 11A5.5 +++ 49IgG1 13 11A5.9 + 43 11A5.11 + 45 11A5.12 + 51 IgG1/IgG2a 76

Example 10 Intracellular Staining of FcRn

THP-1 cells (a human monocytic cell line) and Caco-2 cells (a humanintestinal epithelial cell line) were studied for intracellular stainingof FcRn using purified monoclonal antibodies (mABs) specific to FcRn.Aliquots of 300,000 cells/tube of THP-1 or Caco-2 cells were pelletedand resuspended in 250 μl of BD Cytofix/Cytoperm (BD BiosciencesPharmingen, San Diego, Calif.). The cells were washed twice with 1 ml ofBD Perm/wash solution (BD Biosciences Pharmingen, San Diego, Calif.) andresuspended in the same solution. Alexa fluor 488 (Molecular Probes,Eugene, Oreg.) labeled mABs (1 g/tube) were added to the cells and thecells were incubated for 45 minutes on ice. The cells were washed twicewith BD Perm/wash solution (BD Biosciences Pharmingen, San Diego,Calif.) and resuspended in PBS/1% bovine serum albumin. The cells wereanalyzed by FACS (Beckman Coulter, Inc., Miami Fla.). The results arepresented in FIGS. 9 and 10 and indicated that mABs 3B3.11, 31.1, 4B4.12and 15B6.1 all effectively bound to intra-cellular FcRn in THP-1 cells(FIG. 9), while the 4.13 mAB did not. Similar results were obtained forthe Caco-2 cells (FIG. 10).

Example 11 Intracellular and Surface Staining of Mouse Spleen Cells withAnti-FcRn Mabs

Forceps were used to tease apart cells from the mouse spleen. The cellswere pelleted and resuspended in ACK lysis buffer (8.29 g NH₄Cl, 1 gKHCO₃, 37.2 mg Na₂EDTA, H₂O to a final volume of 1 liter, pH 7.2-7.4)and incubated at room temperature for 5 minutes. The cells were washedthree times with DMEM/5% FBS (Invitrogen, Carlsbad, Calif.). 1×10⁶ cellswere transferred to a microfuge tube and pelleted in a table topmicro-centrifuge. For intracellular staining a fixation andpermeabilization step was performed as described in Example 10. Thecells were resuspended in washing buffer (PBS/1% BSA) containing 20μg/ml mouse isotype control antibody and incubated on ice 20 minutes.The cells were pelleted and Alexa 488 (Molecular Probes, Eugene, Oreg.)labeled mABs (1 μg/tube) in 100 μl washing buffer containing 1 μg/mlisotype control antibody was added to the cells. The cells wereincubated on ice for 40 minutes and then washed twice with washingbuffer. Scatter was gated as macrophages/monocytes enriched populationusing EXPO.32 software. By adjusting forward scatter and size scatter,macrophage/monocytes (unique population with large size and highgranuality) enriched population was analyzed. The cells were analyzed byFACS (Beckman Coulter, Inc., Miami Fla.). The results are presented inFIGS. 11A and 11B indicate that mAB 4B4.12 detected mouse FcRn on thesurface and intracellularly in both spleen cells andmacrophage/monocytes obtained from the spleen cell population.

Example 12 Effect of Anti-FcRn mAB 4B4.12 on Immune Response

Female Balb/c mice, 6-8 weeks old, were immunized with 50 μl of anemulsion of complete Freund's adjuvant mixed 1:1 with ovalbumin. Micewere immunized subcutaneously once on each side of the flank on day 0and boosted on day 10 with 100 μg of ovalbumin/mouse. Mice were treatedby injecting intra-peritoneally either the 4B4.12 mAB specific to FcRnor the isotype control (1813; ATCC1813) antibody (1 mg/ml in PBS/mouse)or PBS. Treatments were administered on day −1, day 0, day 1, and everyother day there after. The mice were bled on day 9 for serum samples andeuthanized on day 16. A maximum serum draw was made after euthanization.The protocol is summarized below in Table 4.

TABLE 4 Treatment Protocol Treatments Every Day 0 other Group# Day −1 IPSC Day +1 day Day +9 Day +10 Day +16 1 4B4.12 4B4.12 OVA + CFA 4B4.124B4.12 Bleed OVA Assays 2 1813 1813 OVA + CFA 1813 1813 Bleed OVA Assays3 PBS PBS OVA + CFA PBS PBS Bleed OVA Assays

Spleens and draining lymph nodes were obtained and weighed in ananalytical balance. The results presented in FIGS. 12 and 12B indicatethat the weight of both the spleen and the draining (inguinal) lymphnode was reduced in the mice treated with the 4B4.12 mAB compared to the2 controls.

Ovalbumin antibody titer was measured by ELISA. Ovalbumin at aconcentration of 10 μg/ml was coated on ELISA plates and blocked withPBS/1% BSA. Titrated serum (starting with 1 to 50 then 2 fold dilutionof 2 μg/ml in PBS/1% BSA) and standard mouse IgG1 (mouse mAB anti-OVA)was added to the plates and incubated at 37° C. for 2 hours. Goatanti-mouse IgG HRP (Pierce, Rockford, Ill.) was added and the plateswere incubated for 30 minutes. TMB solution (KPL, Gaithersburg, Md.) wasadded and the color developed. Optical density was measured at 450 nMusing a microplate reader (Bio-rad, Hercules, Calif.). The results arepresented in FIG. 13 and demonstrate that the 4b4.12 mAB significantlyreduced anti-ovalbumin serum concentration.

Example 13 Effect of 4B4.12 on Catabolism of Synagis in CD1 Mice

CD1 Mice (n=4) (Charles River Laboratories) were injectedintra-peritoneally with Synagis 1 mg/kg. 72 hours later, 4B4.12, MIgG1or PBS were injected intra-peritoneally (20 mg/kg). After 4, 6 and 10days, mouse serum was obtained and Synagis concentration was determinedby ELISA. Anti-human IgG (FAB′)₂ antibody at the concentration of 10g/ml in ELISA coating buffer (Sigma) was coated on ELISA plates at 37°C. for 1 hour. After two washes with PBST, the plates were blocked withPBS/2% BSA for 1 hour at 37° C. Following two washes, serum samples werediluted two fold starting at a 1 to 50 dilution and added to the platesin duplicates (100 μl/well). The plates were incubated for 2 hours at37° C. After three washes with PBST, HRP conjugate of Goat anti-humanIgG Fc was added to the plates and incubated at room temperature for 40minutes. After 4 washes with PBST, TMB substrates (KPL) were added tothe plates and incubate for 5 minutes at room temperature. The colorreaction was stopped with stop solution (KPL) and the plates were readat a microplate reader (Molecular Devices).

The results at day 4 are presented in FIG. 14 and demonstrate the 4B4.12mAB increases catabolism of Synagis compared to control antibody MIgG2aor PBS. The concentration of Synagis over 10 days in the three treatmentgroups is depicted in FIG. 15 and demonstrates that mAb 4B4.12 increasedSynagis catabolism consistently from day 4 through day 10 when comparedto MIgG2a or PBS.

Example 14 Therapeutic Effect of mAB 4B4.12 in a Rat Model forAutoimmune Disease

The experimental autoimmune disease, myasthenia gravis (EAMG), can beinduced in the rat by passive transfer of anti-AchR mAB35 (Socrates etal. Journal of Neuroimmunology. 15:185-194 (1987)). Monoclonal antibody4B4.12 which cross-reacts with rat FcRn was evaluated for its ability toeffect disease status in the EAMG rat model.

4-5 week-old female Lewis rats (75-100 g) were used. Rats were clearlyear-marked. Monoclonal antibodies were administered intra-peritoneally24 hours before the disease induction, on the day of disease inductionand 24 hours after the disease induction. On the day of diseaseinduction, FcRn blocking or control mABs were given firstintra-peritoneally followed by intra-peritoneally injection of mAB35 twohours later. Injection volume was 1 ml. Three groups (6 rats/group) ofrats were used for the experiment: group 1 was treated with mAB 4B4.12,group 2 was treated with 1813 (control mAB), group 3 was treated withPBS. 48 hours after the disease induction, 100 μl of serum was obtainedfrom each rat for the measurement of mAB35 and mouse mABs. The protocolis summarized in Table 5.

TABLE 5 Treatment Protocol Treatments Samples Group # Day −1 Day 0 Day+1 Day +2 1 4B4.12 4B4.12 4B4.12 Bleed 40 mg/kg IP IP followed 40 mg/kgIP for serum lot 2—4.98 mg/ml (2 h later) by mAB35 IP 2 1813 1813 1813Bleed 40 mg/kg IP IP followed 40 mg/kg IP for serum lot 2—4.67 mg/ml (2h later) by mAB35 IP 5 PBS PBS followed PBS Bleed (2 h later) by forserum mAB35 IP

Rats were observed for the signs of disease twice daily 12 hours afterthe disease induction. The following scoring system was used: Grade 0,no symptoms; (1) weak grip, fatigability and sometimes wheezing; (2)general weakness, hunched posture at rest, decreased body weight,tremors; (3) severe weakness, moribund; and (4) death. The protocol issummarized in Table 5. The results are presented in Table 6 and FIG. 16and demonstrate that mAB 4B4.12 decreased disease severity in the EAMGmodel.

TABLE 6 Disease Status Group Disease free Disease 4B4.12 2 4 1813(mIgG2a) 0 6 PBS 0 6

Weight loss or weight gain was determined for rats in each of theexperimental groups. The results are presented in Table 7 and FIG. 17and demonstrate that rats treated with the 4B4.12 mAB lost less weightthan the corresponding control groups.

TABLE 7 Weight Change Group Gained weight Lost weight 4B4.12 3 3 1813(mIgG2a) 0 6 PBS 1 5

Example 15 Effect of Antibodies of the Invention on Human IgG Catabolismin Tg32B Mice

Adult TG32B mice were injected intravenously with 5 mg/kg of biotin-hIgGand 495 mg/kg of human IgG (MP Biomedicals, Irvine, Calif.) at t=0 hours(T₀). Then at 24, 48, 72, 96 and 120 hours, the mice were injectedintravenously with 50 mg/kg of an antibody of the invention. Controlinjections were performed at each timepoint using PBS. Blood sampleswere taken prior to injections at all timepoints, as well as at 168hours. Serum was prepared and stored at −20° C. until an ELISA measuringBiotin-hIgG was performed.

Streptavidin coated plates (Pierce) were rehydrated with three washes(200 μl/well) of PBST (PBS containing 0.05% Tween 20). Serum samples andstandards were diluted in PBS containing 2% BSA (dilution buffer).Sample dilutions were 1:10,000, 1:20,000, 1:30,000 and 1:40,000.Standard was diluted from 200 ng/ml to 1.56 ng/ml in 2 fold dilutions.The plates were incubated at 37° C. for 2 hours followed by washingthree times with PBST. Then the plates were incubated with 100 μl/wellgoat anti-human Fc-HRP conjugate (Pierce) diluted 1:25,000 in dilutionbuffer at room temperature for 30 minutes. After three washes of PBST,100 μl TMB solution (BioFx) was added to the plates and the plates wereincubated in dark at room temperature until appropriate color developed(when the wells of highest standard turn dark blue). Then 100 μl/well of0.25M H₂SO₄ was added to stop the color reaction and OD was measured at450 nM.

The results showed that 3B3.11 significantly reduced the serumconcentration of Biotin-hIgG, indicating the increased catabolism ofhIgG after FcRn blockade (FIGS. 18 & 19).

Example 16 Summary of mABs in Reactivity Across Species

MAB 4B4.12, 3B3.11, 31.1, 4.13 and 3B5.4 were studied in FACS bindingassays and FACS blocking assays for reactivity to FcRn across species.Human FcRn expressing cells (293C11) and monkey FcRn expressing cellswere produced. Rat and mouse FcRn expressing cells were from NeilSimister of Brandeis University. For blocking experiments, FcRnexpressing cells were incubated with Alexa-A488 labeled hIgG1 (100 nM)and various concentrations of mABs (4B4.12, 3B3.11, 31.1, 4.13 and 3B5.4or isotype controls such as IgG1, IgG2a) in pH6 PBS buffer. 45 minuteslater, the cells were analyzed by fluorescence staining and TMFI wascalculated (see Example 6 for detailed method). If the mAB inhibitshIgG1 binding to respective FcRn expressing cells above 30%, this mAb isconsidered a blocking mAB in this species. For binding experiments, FcRnexpressing cells were incubated with Alexa-A488 labeled mABs (4B4.12,3B3.11, 31.1, 4.13 and 3B5.4 or isotype controls such as IgG1, IgG2a) inpH7.4 PBS buffer for 60 minutes. After one wash with PBS buffer, thecells were examined in a Coulter flow cytometer for fluorescencestaining. If the binding of particular mAB to the cells is significantabove isotype control binding (TMFI is 50% higher), this mAb isconsidered capable of binding to such species FcRn. Table 8 and FIG. 20show a summary of the results.

TABLE 8 Summary of mAR for cross reactivity Binding Blocking mAB IsotypeHuman Monkey Rat Mouse Human Monkey Rat Mouse 4B4.12 IgG2a Yes Yes YesYes Yes Yes Yes Yes 3B3.11 IgG1 Yes Yes No Yes Yes Yes No No 31.1 IgG1Yes No No No Yes No No No 4.13 IgG1 Yes No Yes Yes Yes No No No 3B5.4IgG2a Yes Yes Yes Yes Yes Yes Yes No (anti-β2m)

Example 17 Monkey FcRn Transient Transfectants Stained with Anti-hFcRnmABs

Cos1 cells were transfected with monkey FcRn heavy chain (in pcDNA6) andβ2M (pED.dc) with Gene Jammer transfection reagent (Strategene). 48hours later, the cells were harvested and washed once with PBScontaining 0.5% BSA. 5×10⁵ cells were incubated with mABs for 45 minuteson ice. Then the cells were washed once with PBS containing 0.5% BSA.The cells were then incubated with Alexa 488 labeled goat anti-mouse IgG(1:2500 dilution) for 45 minutes on ice. After one wash, the cells wereanalyzed for fluorescence staining in a Coulter flow cytometer. Theresults are expressed as TMFI.

Example 18 Western Blots with Anti-HFcRn mABs

3 μg of soluble human FcRn (Extra-cellular domain of heavy chain andβ2M) was loaded to each lane of a 4-20% Tris-glycine gel (Invitrogen)and was run at 200V for 60 minutes. Then the gel was loaded to a gelblotting apparatus (Xcell II, Invitrogen) with a PVDF membrane(Amersham) and run at 55V for 1 hr at room temperature. Then themembrane was blocked with 5% milk in PBST (PBS plus 0.05% Tween 20) for1 hour. After that, the membrane was incubated with 10 μg/ml of variousmABs overnight at 4° C. After washing twice with PBST, the membrane wasincubated with goat anti-human IgG HRP (Southern Biotech Associates) at1:10,000 dilution for 90 min. After another two washes, the membrane wasdeveloped with a ECL kit (Amersham). The results show that mAB 3B3.11,3B3.16, 3B3.21, 3B3.35, 4.13, 15B6.1 and 31.1 recognized the human FcRnheavy chain while 3B5.4 and 5A4.9 recognized β2M (FIG. 21).

TABLE 9 Biacore analysis of anti-hFcRn mAb 3B3.11 Human FcRn pH 6.0 pH7.4 KD Off-Rate KD Off-Rate mAb (nM) (sec⁻¹) × 10⁴ (nM) (sec⁻¹ × 10⁴)3B3.11 1.17 ± 0.39 1.76 ± 0.79 0.16 (n = 2) 0.0145 (n = 2) 3B3_11 (cyno)3.23 ± 0.14 5.52 ± 5.4  3.24 ± 0.30 2.47 ± 2.3

Example 19 Biacore Analysis of 3B3.11

A CMS chip (Biacore) was coated with approximately 500 RU of solublehuman FcRn or soluble monkey FcRn (diluted 100× into acetate at pH 4.5)using standard amine coupling. Five five-fold serial dilutions ofantibody were made, starting from an initial concentration of 10 μg/mL.Each dilution was passed over the chip in duplicate at 50 l/min for 1minute. The data were solved for a 1:1 binding interaction. Bothbindings at pH 6 and pH 7.4 were examined (FIGS. 22A-D and Table 9).

Example 20 Epitope Mapping of Anti-hFcRn mAbs

Soluble human FcRn and mouse monoclonal antibodies are preparedroutinely in house. All reagents, buffers and chemicals were purchasedform Biacore AB (Uppsala, Sweden) unless otherwise noted.

Instrumentation and Surface Preparation:

Analysis of macromolecular interactions using surface plasmon resonancehas been described in detail (1). A BIACORE 3000 instrument (Biacore AB)was used and all binding interactions were performed at 25° C. Acarboxymethyl-modified dextran (CMS) sensor chip (Biacore AB) was usedfor the analysis. Anti-FcRn monoclonal antibodies was diluted to 1-10μg/mL in 10 mM sodium acetate (pH 5.0) and immobilized to one flow-cellof the sensor chip, using amine coupling as described in (1). Finalimmobilization level was approximately 10000 Resonance Units (RU). Acontrol antibody surface using a separate flow-cell was created usingthe same procedure in the presence of a non-FcRn specific antibody (mAB1745) and served as a reference for the binding studies.

Assay Design:

The amino acid sequence of soluble human FcRn (shFcRn) was synthesizedas a continuous series of 27 peptides, with each peptide extending 20residues in length. These peptides had an overlapping sequence of 10amino acids. The peptides were dissolved in 100% DMSO to a finalconcentration of 1-5 mg/mL. For analysis, the peptide solutions werediluted 100-fold in HBS-N buffer (10 mM HEPES, pH 7.4; 150 mM NaCl) andinjected over the FcRn-specific antibody and reference surfaces for 3minutes at a rate of 20 uL/min. After a 35 s. dissociation phase, thesurface was regenerated by a 30 s pulse of 10 mM glycine (pH 2.0) and a15 s pulse of 1% SDS at a flow rate of 60 uL/min. As a positive control,shFcRn was injected over the specific and control flow-cells before thefirst peptide tested and after the last peptide tested to ensure chipstability. A buffer control (1% DMSO in HBS-N) was also passed over bothflow-cells as a negative control.

Data Evaluation:

The sensorgrams (RU versus time) generated for the control-coated(non-specific mAB) flow-cell were automatically subtracted from theFcRn-coated sensograms. Response at equilibrium (Req) was measured 30 sbefore the end of the injection phase (1). Positive response indicatesspecific binding of the peptide to the specific antibody(Frostell-Karlsson, et al. J. Med. Chem., 43: 1986-1992 (2000)).

Summary of mAb Epitopes

Syn 558: (SEQ ID NO: 24)Ac-SCPHRLREHLERGRGNLEWK-CONH2-----mAB 4B4.12, 4.13 Syn 559:(SEQ ID NO: 25) Ac-ERGRGNLEWKEPPSMRLKAR-CONH2------mAB 4B4.12, 4.13Syn 562: (SEQ ID NO: 26)Ac-CSAFSFYPPELQLRFLRNGL-CONH2---------mAB 3B3.11, 4.13 Syn 544:(SEQ ID NO: 27) Ac-APGTPAFWVSGWLGPQQYLS-CONH2------mAB 31.1

Example 21 Selection and Primary Screening of Fabs

A. Selection Protocols

Soluble Fabs (sFabs) were identified from a phage display library thatdisplays Fab fragments. Four different selections using soluble human(shFcRn) or rat FcRn proteins and 293 C11 cells expressing the humanFcRn protein were carried out. Additional selections were also carriedout using a combination of cells and protein targets using the sameelution strategy as outlined below:

-   -   1) Selections Against Biotinylated shFcRn: Three rounds of        selection against biotinylated shFcRn were carried out with        depletion on streptavidin beads. Phagemid were allowed to bind        to target in acidic binding buffer (pH 6), and were then eluted        with non-specific commercial human IgG (Calbiochem, 401114        http://www.emdbiosciences.com/product/401114) and monoclonal        mouse anti-human FcRn mAb (3B3) in an acidic buffer. After        competitive elution, all remaining bound phage were eluted by        direct bead infection of cells. The eluted phage output was used        as input for next round of selection.    -   2) Selections against non-biotinylated shFcRn: Three rounds of        selection against non-biotinylated hFcRn which were passively        immobilized on a 96 well ELISA plate were carried out with        depletion on BSA coated wells. Phagemid were allowed to bind to        target in acidic binding buffer (pH 6), and then were eluted        with non-specific commercial human IgG and anti-human FcRn mAb        (3B3) in the same acidic buffer. After competitive elution, all        remaining bound phage were eluted by using pH 7.4 buffer as well        by direct infection of cells. The eluted phage output was used        as input for next round of selection.    -   3) Selections Against Anti-Human FcRn Antibody        (17D3)-Immobilized Non-Biotinylated shFcRn: Three rounds of        selection against hFcRn captured using biotinylated 17D3 on        streptavidin beads was carried out. Also included was a step of        depletion using biotinylated 17D3 on streptavidin beads in the        absence of FcRn. Phagemid were allowed to bind to target in        acidic binding buffer (pH 6), and then were eluted with        non-specific commercial human IgG and anti-human FcRn mAb (3B3)        in the same acidic buffer. After competitive elution, all        remaining bound phage were eluted by direct bead infection of        cells. The eluted phage output was used as input for next round        of selection.    -   4) Selections Against hFcRn Expressing Cells: Three rounds of        selection against hFcRn-transfected cells were carried out with        depletion on untransfected parental cells. Phagemid were allowed        to bind to cells in acidic binding buffer (pH 6), and then were        eluted with non-specific human IgG and anti-Fc-Rn mAb in the        same acidic buffer. After competitive elution, all remaining        bound phage were eluted by cell lysis with magnetic streptavidin        beads and subsequent infection of bacteria. The eluted phage        output is used as input for next round of selection. Selection        against both soluble human FcRn protein (shFcRn) and        hFcRn-expressing cells:

Outputs from (1) and (2) and (4) above were used in alternateprotein:cell:protein and cell:protein:cell (Round1:Round2:Round3:Round4) selections using the same elution strategy asabove. ELISA Screening for Fab inhibitors of FcRn.

To identify hFcRn binders, primary screening of round 2 and/or 3 outputsfrom each selection arm described above against biotinylated shFcRn inphage ELISA was carried out. Approximately 768 primary ELISA-positiveFabs on phagemid were re-arrayed, the DNA sequenced, and furthersecondary screened for pH-dependent binding (pH 6 vs. pH 7.5), speciesspecificity (rat vs. human), beta 2 microglobulin binding, and IgGcompetition.

One hundred sixty-one unique phagemids that passed the secondary ELISAscreening had distinct heavy chains. All 161 unique phagemids weresubcloned and expressed as sFabs and screened in a FACS blocking assay.

Blocking of IgG-Fc binding to human FcRn-expressing 293 C11 cellsperformed at 4° C. in an acidic environment resulted in the discovery ofeleven sFabs with antagonistic anti-FcRn properties. All eleven sFabFc-FcRn blockers were reformatted into IgG1 and reformatted as AZallotypes and further characterized in vitro for affinity to solublehuman and rat FcRn (K_(D) determination by SPR method), Fc-FcRn blockingusing FACS analysis (IC₅₀), beta 2 microglobulin binding (by SPR), pHdependent binding and blocking at pH 6 and pH 7.5 to soluble proteinsand cells (human FcRn and rat FcRn in FACS and by SPR).

Example 22 Anti-FcRn Fabs

The CDR sequences of exemplary ant-FcRn Fabs identified in the phagedisplay library selections are shown in Table 10.

TABLE 10 Summary of anti-FcRn phagemid Fab Amino Acid CDR Sequences FabLV-CDR1 LV-CDR2 LV-CDR3 HV-CDR1 HV-CDR2 HV-CDR3 532A- SGSSSNIGSNTVSSDNQRPS AAWDDSLKGWV DYTMS SIWSSGGATVYADSV DIRGSRNWFD M0090-F09(SEQ ID NO: 28) (SEQ ID NO: (SEQ ID NO: 30) (SEQ ID KG (SEQ ID NO: 32)P (SEQ ID NO: 33) 29) NO: 31) 532A- TGTGSDVGSYNLVS GDSQRPS CSYAGSGIYVEYAMG SIGSSGGQTKYADSV LSTGELY M0090-F11 (SEQ ID NO: 34) (SEQ ID NO:(SEQ ID NO: 36) (SEQ ID KG (SEQ ID NO: 38) (SEQ ID NO: 39) 35) NO: 37)532A- RSSQSLLHSNGYNY LVSNKAS MQAQQTPIT (SEQ IYSMT SIVPSGGETSYADSVGHSGVGMDV M0062-C09 LD (SEQ ID NO: 40) (SEQ ID NO: ID NO: 42)(SEQ ID NO: KG (SEQ ID NO: 44) (SEQ ID NO: 45) 41) 43) 532A-RSSQSLLHGNGHTY LVSNRAS MQGLQTPRT FYSMT GIRSSGGSTRYADSV GWGLDAFDVM0064-H04 LD (SEQ ID NO: 46) (SEQ ID NO: (SEQ ID NO: 48) (SEQ ID NO:KG (SEQ ID NO: 50) (SEQ ID NO: 51) 47) 49) 532A- RSSLSLLHSNGYIYL LGSHRASMQPLQTPYT YYHMN VISPSGGVTMYADSV GKAFDI (SEQ M0057-F02 D (SEQ ID NO: 52)(SEQ ID NO: (SEQ ID NO: 54) (SEQ ID NO: KG (SEQ ID NO: 56) ID NO: 57)53) 55) 532A- SGDKLGDKYVS QDNRRPS QAWLSNTASVA FYGMH GIYSSGGITGYADSVGLRTFDY M0084-B11 (SEQ ID NO: 58) (SEQ ID NO: (SEQ ID NO: 60)(SEQ ID NO: KG (SEQ ID NO: 62) (SEQ ID NO: 63) 59) 61) 532A- RASQPVGSYLAGASNRAT QHYGHSFPYT SYAMY RIVPSGGGTMYADSV GMDV (SEQ M0084-B03(SEQ ID NO: 64) (SEQ ID NO: (SEQ ID NO: 66) (SEQ ID NO:QG (SEQ ID NO: 68) ID NO: 69) 65) 67) 532A- RASQSVSSYLA (SEQ DASNRATQQRSNWPLT NYNMS YISPSGGSTWYADSV YHYGMDV M0073-E10 ID NO: 70) (SEQ ID NO:(SEQ ID NO: 72) (SEQ ID NO: KG (SEQ ID NO: 74) (SEQ ID NO: 75) 71) 73)532A- RASQSISNHLV (SEQ DASNRAT QQRSNWPPT YYGMT SISPSGGHTSYADSVKGPEYFFGVY M0056-G05 ID NO: 76) (SEQ ID NO: (SEQ ID NO: 78) (SEQ ID NO:G (SEQ ID NO: 80) (SEQ ID NO: 81) 77) 79) 532A- RASQSVGSYLN (SEQ AAYILQSQQSYSNRIT (SEQ AYNMI SIGPSGGKTVYADSV VRSGFWSGHD M0055-G12 ID NO: 82)(SEQ ID NO: ID NO: 84) (SEQ ID NO: KG (SEQ ID NO: 86) Y (SEQ ID NO: 87)83) 85) 532A- RASQSVSSSYLA GASSRAT QQYGSSPRT HYGMS YIRPSGGKTTYADSVDSWGSFPNDA M0092-D02 (SEQ ID NO: 88) (SEQ ID NO: (SEQ ID NO: 90)(SEQ ID NO: KG (SEQ ID NO: 92) FDI (SEQ ID NO: 89) 91) 93)The DNA sequences of these Fab light chain variable regions (LV) areshown below:

>M0062-C09 LV kappa (SEQ ID NO: 94)CAAGACATCCAGATGACCCAGTCTCCAGACTCCCTGCCCGTCACCCCTGGAGAGCCGGCCTCCATCTCCTGCAGGTCTAGTCAGAGCCTCCTGCATAGTAATGGATACAACTATTTGGATTGGTACCTGCAGAGGCCAGGGCAGTCTCCGCAGCTCCTGATCTATTTGGTTTCTAATCGGGCCTCCGGGGTCCCTGACAGGTTCAGTGGCAGTGGGTCAGGCACAGATTTTACACTGAAAATCAGCAGAGTGGAGGCTGAAGATGCTGGATTTTATTACTGCATGCAAGCTCAACAAACTCCGATCACCTTCGGCCAAGGGACACGACTGGAGATTAAA >M0057-F02 LV kappa(SEQ ID NO: 95) CAAGACATCCAGATGACCTAGTCTCCACTCTCCCTGCCCGTCACCCCTGGAGAGCCGGCCTCCATGTCCTGCAGGTCTAGTCTGAGCCTCCTGCATAGTAATGGATACATCTATTTGGATTGGTACCTGCAGAGGCCAGGACAGTCTCCACAGCTCCTGATGTATTTGGGTTCTCATCGGGCCTCCGGGGTCCCTGACAGGTTCAGTGGCAGTGGGTCAGGCACAGATTTTACACTGAACATCAGCAGAGTGGAGGCGGAGGATGTTGGGGTTTATTACTGCATGCAACCTCTACAAACTCCGTACACTTTTGGCCAGGGGACCAAGCTGGAGATCAAA >M0055-G12 LV kappa(SEQ ID NO: 96) CAAGACATCCAGATGACCCAGTCTCCATCCTCCCTGTCTGCATCTGTAGGAGACAGAGTCACCATCACTTGCCGGGCAAGTCAGAGCGTTGGCAGTTATTTAAATTGGTATCAGCAGAAACCAGGCGAAGCCCCTAAGGCCCTGATCTATGCTGCATACATTTTGCAAAGTGGGGTCCCATCGAGGTTCAGTGGCAGCGGCTCTGGGACAGATTTCACTCTCACCATCAACAGTCTACAACCTGAAGATTTTGCAACTTATTACTGTCAACAGAGTTACAGTAATAGAATCACTTTCGGCCCTGGGACCAGAGTGGATGTCAAA >M0064-H04 LV kappa (SEQ ID NO: 97)CAAGACATCCAGATGACCCAGTCTCCACTCTCCCTGCCCGTCACCCCTGGAGAGCCGGCCTCCATCTCCTGCAGGTCTAGTCAGAGCCTCCTGCACGGAAATGGACACACCTATTTGGATTGGTATCTGCAGAAGCCAGGGCAGTCTCCACAGCTCCTGATCTATTTGGTTTCTAATCGGGCCTCCGGGGTCCCTGACAGGTTCAGTGGCAGTGGATCAGGCACAGATTTTACACTGAAAATCAGCAGAGTGGAGGCTGAAGATGTTGGGGTTTATTACTGCATGCAAGGTCTACAAACTCCGAGGACGTTCGGCCAGGGGACCAAGGTGGAAATCAAA >M0056-G05 LV kappa(SEQ ID NO: 98) CAAGACATCCAGATGACCCAGTCTCCAGCCACCCTGTCTTTGTCTCCAGGGGAAAGAGCCACCCTCTCCTGCAGGGCCAGTCAGAGTATTAGCAACCACTTAGTCTGGTTCCAACAGAAACCTGGCCAGGCTCCCAGGCTCCTCATCTATGATGCATCCAACAGGGCCACTGGCATCCCAGCCAGGTTCAGTGGCAGTGGGTCTGGGACAGACTTCACTCTCACCATCAGCAGCCTAGAGCCTGAAGATTTTGCAGTTTATTACTGTCAGCAGCGTAGCAACTGGCCTCCCACCTTCGGCCAAGGGACACGACTGGAGATTAAA >M0084-B03 LV kappa (SEQ ID NO: 99)CAAGACATCCAGATGACCCAGTCTCCAGCCACCCTGTCTTTGTCTCCAGGGGAAACAGCCACCCTCTCCTGCCGGGCCAGTCAGCCTGTTGGCAGCTACTTAGCCTGGTACCAACAGAAACCTGGCCAGGCTCCCAGGCTCCTCATCTATGGTGCATCCAATAGGGCCACTGGCATCCCAGCCAGGTTCAGTGGCAGTGGGTCTGGGACAGACTTCACTCTCGCCATCAGCAGCCTGGAGCCTGAAGATTTTGGAGTGTATTACTGTCAGCACTATGGTCACTCACCTCCGTACACTTTTGGCCAGGGGACCAAGCTGGAGATCAAA >M0092-D02 LV kappa (SEQ ID NO: 100)CAAGACATCCAGATGACCCAGTCTCCAGGCACCCTGTCTTTGTCTCCAGGGGAAAGAGCCACCCTCTCCTGCAGGGCCAGTCAGAGTGTTAGCAGCAGCTACTTAGCCTGGTACCAGCAGAAACCTGGCCAGGCTCCCAGGCTCCTCATCTATGGTGCATCCAGCAGGGCCACTGGCATCCCAGACAGGTTCAGTGGCAGTGGGTCTGGGACAGACTTCACTCTCACCATCAGCAGACTGGAGCCTGAAGATTTTGCAGTGTATTACTGTCAGCAGTATGGTAGCTCACCTCGGACGTTCGGCCAAGGGACCAAGGTGGAAATCAAA >M0090-F09 LV lambda (SEQ ID NO: 101)CAGAGCGCTTTGACTCAGCCACCCTCAGCGTCTGAGACCCCCGGGCAGAGAGTCACCATCTCTTGTTCTGGAAGCAGCTCCAACATCGGAAGTAATACTGTAAGCTGGTACCAGCAGCTCCCAGGAACGGCCCCCAAACTCCTCATCTATAGTGATAATCAGCGGCCCTCAGGGGTCCCTGACCGATTCGCTGGCTCCAAGTCTGGCACCTCTGCCTCCCTGGCCATCAGTGGGCTCCAGTCTGAGGATGAGGCTGAATATCACTGTGCAGCATGGGATGACAGCCTGAAGGGTTGGGTGTTCGGCGGAGGGACAAAGCTGACCGTCCTA >M0084-B11 LV lambda (SEQ ID NO: 102)CAGAGCGCTTTGACTCAGACACCCTCAGTGTCCGTGTCCCCCGGACAGACAGCCACCATCACCTGCTCTGGAGATAAATTGGGGGATAAGTATGTTTCTTGGTTTCAACAGAAGCCAGGCCAGTCCCCTATCCTACTCCTTTATCAAGACAACAGGCGGCCCTCTGGGATCCCTGAACGATTCTCTGGCTCCAATTCTGGGAACACAGCCTCTCTGACCATCAGCGGGACCCAGGCTATGGATGAGGCTGACTACCACTGTCAGGCGTGGCTCAGCAATACTGCTTCCGTGGCATTCGGCGGAGGGACCAGGCTGACCGTCCTC >M0073-E10 LV kappa (SEQ ID NO: 103)CAAGACATCCAGATGACCCAGTCTCCAGCCACCCTGTCTTTGTCTCCAGGGGAAAGAGCCACCCTCTCCTGCAGGGCCAGTCAGAGTGTTAGCAGCTACTTAGCCTGGTACCAACAGAAACCTGGCCAGGCTCCCAGGCTCCTCATCTATGATGCATCCAACAGGGCCACTGGCATCCCAGCCAGGTTCAGTGGCAGTGGGTCTGGGACAGACTTCACTCTCACCATCAGCAGCCTAGAGCCTGAAGATTTTGCAGTTTATTACTGTCAGCAGCGTAGCAACTGGCCCCTCACTTTCGGCGGAGGGACCAAGGTGGAGATCAAA >M0090-F11 LV lambda (SEQ ID NO: 104)CAGAGCGTCTTGACTCAGCCTGCCTCCGTGTCGGGGTCTCCTGGACAGTCGATCACCATCTCCTGCACTGGGACCGGGAGTGATGTTGGAAGTTATAACCTTGTCTCCTGGTACCAAAAGTACCCCGGCAAAGCCCCCAAACTCATCATTTATGGGGACAGTCAGCGGCCCTCGGGACTTTCTAGTCGCTTCTCTGGCTCCAAGTCTGGCAACTCGGCCTCCCTGACAATCTCTGGGCTCCAGGCTGAGGACGAGGCTGATTATTACTGTTGCTCATATGCAGGTAGTGGCATTTACGTCTTTGGCAGTGGGACCAAGGTCACCGTCCTA

Example 23 Binding of sFabs and Antibodies to FcRn

To further characterize the Fabs and their respective IgG1, SPR8500/BIACORE™ analysis was performed on eleven exemplary antagonsiticanti FcRn antibody clones that were positive for FcRn binding todetermine the K_(D). Exemplary SPR 8500/BIACORE™ data is provided inTables 2 and 3. SFabs and antibodies (IgG) were tested for their abilityto bind to human FcRn (hFcRn) or rat FcRn (rat FcRn) and pH 6 and 7.5.Binding was measured by SPR 8500 and by BIACORE™ and is expressed byK_(D) values (nM). The binding of 8 clones was observed to be pHindependent and 3 pH dependent.

TABLES 11A through E Summary of in vitro SPR 8500 binding data (K_(D)(nM)) of FcRN binding sFabs; On and Off Rate Analyses A. Binding DataAntagonistic anti-FcRN IgG data SPR 8500 SPR 8500 SPR 8500 SPR 8500soluble Fabs sol FAB sol FAB sol FAB sol FAB sol hFcRn sol hFcRn sol ratFcRn sol rat FcRn Clone # K_(D) nM @ pH 6 K_(D) nM @ pH 7.5 K_(D) nM @pH 6 K_(D) nM @ pH 7.5 532A-M0090-F11 9.2 19.1 31.2 9.9 532A-M0064-H0428 25.9 no binding no binding 532A-M0090-F09 5.7 no binding no bindingno binding (pH dependent) 532A-M0084-B03 No fit no binding no binding nobinding (pH dependent) 532A-M0062-C09 25 no binding no binding nobinding (pH dependent) 532A-M0055-G12 12 39.7 no binding no binding532A-M0056-G05 13.6 18.1 no binding no binding 532A-M0084-B11 17.4 19.6no binding no binding 532A-M0092-D02 3.9 18.7 no binding no binding532A-M0073-E10 82 9.7 no binding no binding 532A-M0057-F02 29 11.3 nobinding no binding B. hFcRn pH6 kon koff KD 17D3 2.77E+05 4.30E−041.3E−09 3B3 3.82E+06 1.31E−03 3.4E−10 Fcl — — — hIgG Myeloma — — — hIgGplasma 4.32E+03 2.31E−03 5.3E−07 X0002-G07 2.06E+04 1.24E−04 8.0E−09M0055-G12 1.27E+06 1.53E−02 1.2E−08 M0057-F02 1.48E+05 4.26E−03 2.9E−08M0062-C09 9.44E+04 2.38E−03 2.5E−08 M0064-H04 1.29E+05 3.88E−03 2.8E−08M0073-E10 3.36E+05 2.75E−02 8.2E−08 M0090-F11 9.68E+04 8.97E−04 9.2E−09X0002-A07 — — — C. hFcRn pH 7.4 kon koff KD 17D3 3.24E+05 5.23E−041.61E−09 3B3 2.97E+05 1.75E−03 5.93E−10 Fcl — — — hIgG Myeloma — — —hIgG plasma — — — X0002-G07 — — — M0055-G12 2.01E+05 7.96E−03 3.97E−08M0057-F02 3.25E+05 3.67E−03 1.19E−08 M0062-C09 — — — M0064-H04 1.55E+054.02E−03 2.59E−08 M0073-E10 3.59E+05 3.49E−03 9.71E−09 M0090-F115.94E+04 1.13E−03 1.91E−08 X0002-A07 — — — D. rat FcRn pH 6 kon koff KD17D3 1.74E+04 6.03E−03 3.40E−07 3B3 5.83E+05 1.04E−03 1.50E−09 Fcl2.08E+05 3.29E−03 1.58E−08 hIgG Myeloma 1.30E+05 1.27E−03 9.66E−09 hIgGplasma 9.13E+04 2.42E−03 2.66E−08 X0002-G07 9.70E+04 8.62E−04 8.90E−09M0055-G12 — — — M0057-F02 — — — M0062-C09 — — — M0064-H04 — — —M0073-E10 — — — M0090-F11 1.84E+04 5.73E−04 3.12E−08 X0002-A07 — — — E.rat FcRn pH 7.4 kon koff KD 17D3 — — — 3B3 — — — Fcl — — — hIgG Myeloma— — — hIgG plasma — — — X0002-G07 — — — M0055-G12 — — — M0057-F02 — — —M0062-C09 — — — M0064-H04 — — — M0073-E10 — — — M0090-F11 2.75E+047.40E−04 9.95E−09 X0002-A07 — — —

TABLE 12A through E Summary of in vitro SPR 8500 binding data (K_(D)(nM)) of FcRN binding antibodies; On and Off Rate Analyses A. BindingData Antagonistic anti-FcRn IgG data SPR 8500 SPR 8500 SPR 8500 SPR 8500Format IgG IgG IgG IgG hFcRn hFcRn ratFcRn ratFcRn Clone # K_(D) @ pH 6K_(D) @ pH 7.5 K_(D) @ pH 6 K_(D) @ pH 7.5 532A-M0090-F11 2.44 10.8 9.89.14 532A-M0064-H04 6.82 12.5 31 no binding 532A-M0090-F09 3.64 No fit13.9 no binding (pH dependent) 532A-M0084-B03 2.99 No fit 29.6 nobinding (pH dependent) 532A-M0062-C09 29.5 No fit no fit no binding (pHdependent) 532A-M0055-G12 3.1 10.2 16 no binding 532A-M0056-G05 2.48 2.122.9 no binding 532A-M0084-B11 3.3 2.59 6.43 no binding 532A-M0092-D0217.9 24.2 30.2 no binding 532A-M0073-E10 No fit No fit No fit no binding532A-M0057-F02 NA NA NA no binding B. hFcRn pH 6 Kon Koff KD M62-C9(Fab) 8.12E+04 1.60E−03 1.97E−08 M90-F11(Fab) 9.21E+04 5.63E−04 6.11E−09M62-C09 (IgG) 2.36E+05 6.95E−03 2.95E−08 M90-F11 (IgG) 1.02E+06 2.48E−032.44E−09 3B3 2.30E+06 9.40E−04 4.09E−10 17D3 8.17E+04 1.81E−04 2.22E−09M92-D2 3.87E+04 6.92E−04 1.79E−08 M56-G05 1.13E+05 2.80E−04 2.48E−09M84-B03 1.14E+05 3.40E−04 2.99E−09 SA-A08 — — — FCI — — — human IgGMyeloma — — — human IgG plasma 3.89E+04 6.85E−04 1.76E−08 X11-5 — — —M55-G12 7.49E+04 2.32E−04 3.10E−09 M73-E10 — — — M84-B11 7.53E+042.48E−04 3.30E−09 M64-H04 1.04E+05 7.06E−04 6.82E−09 M90-F09 3.14E+051.14E−03 3.64E−09 C. hFcRn pH 7.4 Kon Koff KD M90-F11(Fab) 9.12E+046.45E−04 7.08E−09 M90-F11 (IgG) 1.59E+05 1.73E−03 1.08E−08 SA-A08 — — —FCI — — — M64-B11 1.31E+05 3.41E−04 2.59E−09 M64-H04 2.17E+05 2.71E−031.25E−08 M73-E10 — — — M55-G12 7.78E+04 7.97E−04 1.02E−08 X11-5 — — —M62-C09 — — — M62-C09 IgG — — — M84-B03 — — — M56-G05 4.14E+05 8.68E−042.10E−09 M90-F09 — — — 3B3 3.41E+06 2.30E−03 6.75E−10 M92-D2 8.16E+041.98E−03 2.42E−08 17D3 1.21E+05 2.42E−04 2.01E−09 human IgG Myeloma — —— human IgG plasma — — — D. rat FcRn pH 6 Kon Koff KD M90-F11 (IgG)1.19E+05 1.17E−03 9.80E−09 M90-F11(Fab) 4.30E+04 8.72E−04 2.03E−08M90-F09 3.21E+05 4.46E−03 1.39E−08 M62-C09 (Fab) — — — M62-C09 — — —M64-H04 7.80E+04 2.42E−03 3.10E−08 M84-B11 3.14E+05 2.02E−03 6.43E−09M73-E10 — — — M55-G12 1.99E+05 3.20E−03 1.60E−08 X11-5 — — — M84-B031.56E+05 4.63E−03 2.96E−08 M56-G05 4.78E+04 1.09E−03 2.29E−08 M92-D24.93E+04 1.49E−03 3.02E−08 M55-G12 1.99E+05 3.20E−03 1.60E−08 3B3 — — —human IgG plasma 2.33E+05 1.42E−03 6.12E−09 human IgG Myeloma — — — FCI— — — SA-A08 — — — E. rat FcRn pH 7.4 Kon Koff KD M90-F11 1.17E+063.84E−03 3.29E−09 M90-F11 (IgG) 1.25E+05 1.14E−03 9.14E−09 SA-A08 — — —FCI — — — M84-B11 — — — M64-H04 — — — M73-E10 — — — M55-G12 — — — X11-5— — — M62-C09 — — — M62-C09 (IgG) — — — M84-B03 — — — M56-G05 — — —M90-F09 — — — 3B3 — — — M92-D2 — — — 17D3 — — — human IgG Myeloma — — —human IgG plasma — — —

Example 24 IC₅₀ Values of sFabs and Antibodies

The sFabs and IgG antibodies of eleven exemplary antagonistic anti-FcRnclones that were positive for FcRn binding were tested in an in vitromodel for their ability to block non-specific human IgG-Fc binding toFcRn. Cultures of 293 C11 cells expressing human FcRn (hFcRn) or ratFcRn (rat FcRn) were treated with an sFab or IgG1 of a binding-positiveclone, a positive control anti-rat FcRn antibody (1G3), a positivecontrol anti-human FcRn antibody (3B3), or a SA-A2 negative control. Thecell cultures were treated with ALEXAFLUOR® labeled non-specific IgG-Fcand incubated at 4° C. in pH 6 buffer conditions. The amount ofIgG-Fc-FcRn binding was determined. Results of exemplary sFabs and/orthe respective IgGs are presented in Table 13. The IC₅₀ values weredetermined by flow cytometry (i.e., FACS) and are expressed in nM.

TABLE 13 Summary of in vitro FACS inhibition data (IC50 (nM)) of FeRnbinding antibodies Antagonistic anti-FcRN IgG data FACS FACS FACS FACS(blocking) (blocking) (blocking) (blocking) IC50 sol FAB sol FAB IgG IgGhFcRn rat FcRn hFcRn rat FcRn (cells) (cells) (cells) (cells) IC50 nMIC50 nM IC50 nM IC50 nM Clone # @ pH 6 @ pH 6 @ pH 6 @ pH 6532A-M0090-F11 13 6481 2.6 4.9 532A-M0064-H04 63 no 1.8 20 blocking532A-M0090-F09 645 no 4.6 5.5 (pH dependent) blocking 532A-M0084-B03 754no 1.8 91 (pH dependent) blocking 532A-M0062-C09 35 no 3.9 148 (pHdependent) blocking 532A-M0055-G12 228 no 1.7 30 blocking 532A-M0056-G05337 no 1.4 18 blocking 532A-M0084-B11 355 no 1.9 25 blocking532A-M0092-D02 271 no 1.2 15 blocking 532A-M0073-E10 110 no 377 161blocking 532A-M0057-F02 70 no NA NA (amber stop) blocking Streptavidinbinder NA NA 562 101 SA-A2 IgG (negative control) lead 3B3 mouse 9.7anti-human FcRn IgG lead IG3 mouse NA NA 1.5 anti-rat FcRn IgG

Example 25 Efficacy Testing of FcRn Binding Antibodies in Animals

Experiments with human FcRn Knock-in Tg32B transgenic mice showed thatfour consecutive daily intravenous doses of M90-F11 (also referred to asM090-F11 and M0090-F11) IgG significantly reduced the serum half-life ofhuman IgG tracer (biotinylated hIgG) at all doses tested (50, 20, 10 and5 mg/kg) (FIGS. 23 & 24). At 50 mg/kg, four iv injections of M55-G12only moderately reduced the serum half-life of tracer hIgG while M84-B11was not efficacious (FIG. 23). An experiment with single doses ofM90-F11 (20 mg/kg and 5 mg/kg) showed moderate reduction of Biotin-hIgG1tracer in the serum of TG32B mice (FIG. 25). The protocol used fortesting anti-FcRn IgGs in transgenic mice was:

1) Administer 500 mg/kg tracer hIgG intravenously at time 0(approximately 1% is biotinylated for quantitation purposes)

2) Anti-FcRn antibodies given intravenously at 24, 48, 72, 96 and 120 hrat 50, 20, 10 and 5 mg/kg

3) Blood samples collected at 24, 48, 72, 96, 120 and 168 hours

4) Quantitate hIgG in serum by ELISA

Based on the Tg mouse model in vivo data, M90-F11 was chosen as leadcandidate for further lead optimization. The 10 germline changes thatwere introduced into the M90-F11 light chain is given below and in FIG.29. The one germline changes that was required in the heavy chain wasnot introduced, however the allotype of the heavy chain was changed fromAZ to F allotype.

LIGHT CONSTANT S  Q  P  K  A  N  P  T  V  T  L  F  P  P  S  S  E  E  L  Q  A CONST:AGTCAGCCCAAGGCCAACCCCACTGTCACTCTGTTCCCGCCCTCCTCTGAGGAGCTCCAAGCC GRMLN:GGTCAGCCCAAGGCCAACCCCACGGTCACTCTGTTCCCGCCCTCCTCTGAGGAGCTCCAAGCC G  Q  P  K  A  N  P  T  V  T  L  F  P  P  S  S  E  E  L  Q  A N  K  A  T  L  V  C  L  I  S  D  F  Y  P  G  A  V  T  V  A  W CONST:AACAAGGCCACACTAGTGTGTCTGATCAGTGACTTCTACCCGGGAGCTGTGACAGTGGCCTGG GRMLN:AACAAGGCCACACTAGTGTGTCTGATCAGTGACTTCTACCCGGGAGCTGTGACAGTGGCTTGG N  K  A  T  L  V  C  L  I  S  D  F  Y  P  G  A  V  T  V  A  W K  A  D  G  S  P  V  K  A  G  V  E  T  T  K  P  S  K  Q  S  N CONST:AAGGCAGATGGCAGCCCCGTCAAGGCGGGAGTGGAGACCACCAAACCCTCCAAACAGAGCAAC GRMLN:AAGGCAGATGGCAGCCCCGTCAAGGCGGGAGTGGAGACGACCAAACCCTCCAAACAGAGCAAC K  A  D  G  S  P  V  K  A  G  V  E  T  T  K  P  S  K  Q  S  N N  K  Y  A  A  S  S  Y  L  S  L  T  P  E  Q  W  K  S  H  R  S CONST:AACAAGTACGCGGCCAGCAGCTACCTGAGCCTGACGCCCGAGCAGTGGAAGTCCCACAGAAGC GRMLN:AACAAGTACGCGGCCAGCAGCTACCTGAGCCTGACGCCCGAGCAGTGGAAGTCCCACAGAAGC N  K  Y  A  A  S  S  Y  L  S  L  T  P  E  Q  W  K  S  H  R  S Y  S  C  Q  V  T  H  E  G  S  T  V  E  K  T  V  A  P  A  E  C  S CONST:TACAGCTGCCAGGTCACGCATGAAGGGAGCACCGTGGAGAAGACAGTGGCCCCTGCAGAATGCTCTGRMLN:TACAGCTGCCAGGTCACGCATGAAGGGAGCACCGTGGAGAAGACAGTGGCCCCTACAGAATGTTCA Y  S  C  Q  V  T  H  E  G  S  T  V  E  K  T  V  A  P  T  E  C  SCONST Amino acid (SEQ ID NO: 107) CONST Nucleic acid (SEQ ID NO: 108)GRMLN Nucleic acid (SEQ ID NO: 110) GRMLN Amino acid (SEQ ID NO: 109)HEAVY Amino Acid (SEQ ID NO: 111) HEAVY Nucleic Acid (SEQ ID NO: 112)GRMLN Nucleic Acid (SEQ ID NOS: 114 and 239, respectively)GRMLN Amino Acid (SEQ ID NOS: 113 and 240, respectively)HEAVY:V:V3-23; J:JH1                              FR1-H E  V  Q  L  L  E  S  G  G  G  L  V  Q  P  G  G  S  L  R  L  S  C HEAVY:GAAGTTCAATTGTTAGAGTCTGGTGGCGGTCTTGTTCAGCCTGGTGGTTCTTTACGTCTTTCTTGCGRMLN:GAGGTGCAGCTGTTGGAGTCTGGGGGAGGCTTGGTACAGCCTGGGGGGTCCCTGAGACTCTCCTGT E  V  Q  L  L  E  S  G  G  G  L  V  Q  P  G  G  S  L  R  L  S  C                           CDR1-H A  A  S  G  F  T  F  S   E  Y  A  M G    W  V  R  Q  A  P  G  K  GHEAVY:GCTGCTTCCGGATTCACTTTCTCT GAGTACGCTATGGGT TGGGTTCGCCAAGCTCCTGGTAAAGGTGRMLN:GCAGCCTCTGGATTCACCTTTAGC AGCTATGCCATGAGC TGGGTCCGCCAGGCTCCAGGGAAGGGG A  A  S  G  F  T  F  S   S  Y  A  M  S   W  V  R  Q  A  P  G  K  G  FR2-H                            CDR2-H L  E  W  V  S   S  I  G  S  S  G  G  Q  T  K  Y  A  D  S  V  K  GHEAVY:TTGGAGTGGGTTTCT TCTATCGGTTCTTCTGGTGGCCAGACTAAGTATGCTGACTCCGTTAAAGGTGRMLN:CTGGAGTGGGTCTCA GCTATTAGTGGTAGTGGTGGTAGCACATACTACGCAGACTCCGTGAAGGGC L  E  W  V  S   A  I  S  G  S  G  G  S  T  Y  Y  A  D  S  V  K  G                 FR3-H R  F  T  I  S  R  D  N  S  K  N  T  L  Y  L  Q  M  N  S  L  R  A HEAVY:CGCTTCACTATCTCTAGAGACAACTCTAAGAATACTCTCTACTTGCAGATGAACAGCTTAAGGGCTGRMLN:CGGTTCACCATCTCCAGAGACAATTCCAAGAACACGCTGTATCTGCAAATGAACAGCCTGAGAGCC R  F  T  I  S  R  D  N  S  K  N  T  L  Y  L  Q  M  N  S  L  R  A                                   CDR3-H                FR4-H E  D  T  A  V  Y  Y  C  A  R   L  S  T  G  E  L  Y   W  G  Q  G  THEAVY:GAGGACACGGCCGTGTATTACTGTGCGAGA CTCTCAACAGGGGAGCTCTAC TGGGGCCAGGGCACCGRMLN:GAGGACACGGCCGTATATTACTGTGCGAAA GA................TAC TGGGGCCAGGGCACC E  D  T  A  V  Y  Y  C  A  K                        W  G  Q  G  T      FR4-H  L  V  T  V  S  S HEAVY: CTGGTCACCGTCTCAAGC GRMLN:CTGGTCACCGTCTCATCA  L  V  T  V  S  S (a, z)ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTS (f)------------------------------------------------ (a, z)GVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKK (f)------------------------------------------------R (a, z)VEPKSCDKTHTCFPCAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVV (f)------------------------------------------------- (a, z)DVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDW (f)------------------------------------------------- (a, z)LNGKEYKCKVSNKALPY   ATISKAKGQPREPQVYTLPPSPREPQVYT (f)------------------------------------------------- (a, z)LPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLD (f)-----E-M----------------------------------------- (a, z)SDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK* (f)-------------------------------------------------(a, z) (SEQ ID NO: 115) (f) (SEQ ID NO: 116)

Example 26 Germlining, Reformatting and Affinity Maturation of ParentalClone M90-F11

Allotype variation of IgG is shown in FIG. 30, the three amino acidchanges (highlighted in bold) from AZ to F allotype were introduced togermlined M90-F11 IgG which already had 10 amino acid changes as part ofgermlining in the light chain.

The parental clone M90-F11 as germ lined had 10 amino acid changes inthe light chain and as part of lead optimization the germlined clone wasreformatted to IgG which had sequences for F allotype in the heavy chainFc region. In total there were 13 amino acid changes as compared toparent M90-F11, the reformatted clone was nucleotide sequence optimizedfor expression in CHO cell lines. Nucleotide sequence/Geneart optimizedclone was given a DX-2500 name, which was used for making stable pool.Parental M90-F11, Germlined M90-F11 (GL) and DX-2500 were characterizedin vitro by Biacore and FACS to assess binding and blocking ability.

Tables 14 and 15 contain the results of Biacore and FACS analysiscomparing the highly purified, parental, germlined and reformattedIgG's:

TABLE 14 Biacore analysis: hFcRn immobilized on the chip and IgG wereflowed over the chip and FACS analysis (IC₅₀) Antagonistic anti-FcRnantibody data FACS biacore biacore biacore biacore biacore biacore(blocking) IgG IgG IgG IgG IgG IgG IgG hFcRn hFcRn hFcRn hFcRn hFcRnhFcRn hFcRn K_(on) K_(off) K_(D) K_(on) K_(off) K_(D) IC50 nM Clone #@pH 6 @pH 6 @pH 6 @pH 7.4 @pH 7.4 @pH 7.4 @pH 6 532A-M0090-F11 2.13E+062.52E−04 1.18E−10 9.09E+05 7.02E−04 7.72E−10 0.43 532A-M0090-F114.45E+06 7.64E−04 1.72E−10 9.96E+05 7.76E−04 7.79E−10 0.38 (germlined LCchanges) DX-2500 (germlined 2.11E+06 3.36E−04 1.60E−10 1.26E+06 3.38E−042.68E−10 0.65 LC & allotype HC changes)

TABLE 15 Biacore analysis: IgG immobilized on the chip and hFcRn wereflowed over the chip. Antagonistic anti-FcRn antibody data biacorebiacore biacore biacore biacore biacore IgG IgG IgG IgG IgG IgG hFcRnhFcRn hFcRn hFcRn hFcRn hFcRn K_(on) K_(off) K_(D) K_(on) K_(off) K_(D)Clone # @pH 6 @pH 6 @pH 6 @pH 7.4 @pH 7.4 @pH 7.4 532A-M0090-F113.03E+05 3.12E−03 1.03E−08 1.81E+05 3.73E−03 2.05E−08 532A-M0090-F115.74E+05 1.72E−02 2.99E−08 4.33E+05 1.52E−02 3.52E−08 (germlined LCchanges) DX-2500 (germlined 6.42E+05 1.77E−02 2.76E−08 3.72E+05 7.52E−022.02E−08 LC & allotype HC changes)

Previous experience with anti-FcRn monoclonal antibody suggested thatthe Koff at pH 7.4 is very critical for in vivo efficacy of theantibody, it became apparent during biacore analysis that when theantibody was immobilized on the chip and target hFcRn was flowed overthe chip, the Koff was much faster for germlined and DX-2500 antibody atboth pH 6 & 7.4. A decision was made to affinity mature the germlinedM90-F11 to select for clones with improved Koff value over DX2500.

A parallel approach was used to affinity mature the germlined M90-F11.Three different libraries (LC shuffled, CDR 1 & 2 and CDR 3 library)were built and are depicted in FIG. 26. A germlined light chain was usedto build library 2 and 3 in order to avoid further sequence optimizationafter selecting the affinity matured lead.

Selection Protocols

Soluble Fabs (sFabs) were identified from the affinity matured M90-F11phagemid display library that displays Fab fragments. Two differentselections using soluble human (shFcRn) and 293 C11 cells expressing thehuman FcRn protein were carried out using three different affinitymatured libraries. Additional selections were also carried out using acombination of cells and protein targets using the same elution strategyas outlined below:

-   -   i) Selections against biotinylated shFcRn: Two rounds of        selection against biotinylated shFcRn were carried out with        depletion on streptavidin beads. Phagemid were allowed to bind        to target in acidic binding buffer (pH 6), and were then eluted        with parental M90-F11 IgG in an pH 7.4 buffer. After competitive        elution/wash, all remaining bound phage were eluted by direct        bead infection of cells. The eluted phage output was used as        input for next round of selection. Round 2 output was used in        alternate round 3 selection against hFcRn-transfected cells        followed by a fourth round selection using biotinylated shFcRn        selections using the same elution strategy.    -   ii) Selections against hFcRn expressing cells: Two rounds of        selection against hFcRn-transfected cells were carried out.        Phagemid were allowed to bind to cells in acidic binding buffer        (pH 6) at 4 degree, and were then eluted with parental M90-F11        IgG in an pH 7.4 buffer. After competitive elution/wash, all        remaining bound phage were eluted by cell lysis with magnetic        streptavidin beads and subsequent infection of bacteria. The        eluted phage output is used as input for next round of        selection. Two additional rounds of selection against        biotinylated shFcRn were carried out as described in (i).

ELISA Screening for Fab Inhibitors of FcRn

To identify hFcRn binders, primary screening of round 3 and 4 outputsfrom each selection arm (4 per library) against biotinylated shFcRn inphage ELISA was carried out at pH 6 & 7.4. Approximately 1152 primaryELISA-positive Fabs on phagemid were screened and DNA sequenced.

One hundred seventy eight unique phagemids from three affinity maturedlibraries (16 from light chain shuffled library, 46 from CDR 1 & 2library and from 116 CDR3 library) that were pH independent binders tohFcRn were selected and subcloned for expression as sFabs.

15 out of 16 phagemid clones screened from LC library had same CDR asthe parent M90-F11 suggesting selection and screening strategy wasbiased in enriching for the parental clones. Affinity matured Sol FABclones (˜165) were subjected to high throughput SPR analysis and rankedby pH 7.4 off-rate and by pH 6 KD values and there were 21 affinitymatured clones from CDR3 library and one clone from CDR1 & 2 librarythat were better than germlined M90-F11. Based on the high throughputSPR screening data, affinity matured M0159-009 clone from CDR 1 & 2library was swapped into HV CDR 1 & 2 position of the affinity maturedM0157-H04 and M0157-E05 from CDR3 library. The constructed two hybridclones M0171-A01 (also referred to as M171-A01) and M0171-A03 (alsoreferred to as M171-A03) had complete affinity matured HV CDR 1, 2 & 3with germlined M90-F11 LC sequences.

In total there were 24 sFAB clones (parental and Germlined M90-F11, 19from CDR3 library, 1 from CDR 1& 2 library and 2 hybrid clones) thatwere sequenced, purified in medium scale and ranked by repeated SPRanalysis (Table 16) and confirmed their antagonistic anti-FcRnproperties in an Fc-FcRn blocking assay using FACS analysis.

TABLE 16 Top 22 affinity matured sol FAB binding kinetics, ranking andHV-CDR sequences (“HV-CDR1,”, “HV-CDR2,” and “HV-CDR3” sequencesdisclosed as SEQ ID NOS 117-140, 191-214, and 215-238, respectively)

TABLE 16A Sequences corresponding to Table 16

All 22 sFAB clones were reformatted to IgG but only 8 IgG wereexpressed, purified and subjected to Flexchip analysis at pH 6 & 7.4.Based on the Flexchip SPR 8500 data the following 4 affinity matured IgGclones were selected for further in vitro (Biacore analysis) and in vivostudy in hFcRn transgenic mouse model.

Table 17A shows the total number of amino acid changes in the HV-CDR1 &2or 3 of the 4 affinity matured IgG in comparison to the parental orDX2500 clone.

TABLE 17A Top 4 affinity matured IgG LV & HV-CDR sequences and # ofmutation compared to parent M90-F11

*10 Germline changes, 3 changes due to AZ to F allotype switch + HV-CDRmutation

TABLE 17 A1 SEQ ID NOs corresponding to Table 17A LV- LV- LV- HV- HV-HV- SEQ ID NOs CDR1 CDR2 CDR3 CDR1 CDR2 CDR3 Parent M90-F11 141 142 143144 145 146 Dx-2500 147 148 149 150 151 152 532A-M0171-A03 153 154 155156 157 158 532A-M0171-A01 159 160 161 162 163 164 532A-M0171-A07 165166 167 168 169 170 532A-M0171-B04 171 172 173 174 175 176Biacore analysis of the 4 affinity matured clone done at pH 7.4 byimmobilizing the IgG on the chip and hFcRn flowed over and their rawdata and fold improvement (K_(off) and K_(D)) over DX-2500 and parentalM90-F11 clone is presented in Table 17B.

TABLE 17B Top 4 affinity matured IgG binding kinetics, fold improvementover DX-2500 & Parent M90-F11 K off Fold K_(D) Fold improvementImprovement Comparison of Biacore Data done at pH 7.4 over over Ka s-1Clone # + SPR Method M-1 Kd s-1 KD (M) DX2500 M90-F11 DX2500 M90-F11M171-A01 IgG Biacore 1.26E+05 1.92E−04 1.52E−09 103 16 58 12 M171-A03IgG Biacore 1.42E+05 2.84E−04 2.00E−09 69 11 44 9 M159-A07 IgG Biacore1.27E+05 6.88E−04 5.40E−09 29 4 16 3 M161-B04 IgG Biacore 1.21E+058.57E−04 7.06E−09 23 3 12 3 M90-F11 parental Biacore 1.61E+05 2.99E−041.86E−08 7 1 5 1 DX-2500 Biacore 2.24E+05 1.97E−04 8.79E−08 1 0.15 10.21

The protocol used for testing affinity matured anti-FcRn IgG and sol FABin hFcRn transgenic mice was:

-   -   6 groups (1 placebo, 4 IgG, 1 Fab. 4 mice/group) [0460]        Intravenous dose of 495 mg/kg hIgG+5 mg/kg biotin-hIgG at time=0        hr    -   Intravenous dose of 5 or 20 mg/kg of Ab (1.67 or 6.67 mg/kg of        Fab) at time=24 hr:    -   M171-A01-IgG,    -   M171-A03-IgG,    -   M159-A07-IgG,    -   M161-B04-IgG or    -   S32A-M171-A01-Fab    -   Blood samples collected at 24 (pre-dose), 30, 48, 72, 96, 120        and 168 hr.    -   Biotin-hIgG serum levels quantified using a streptavidin        capture/Fc detection ELISA and total IgG quantified using an Fab        capture/Fc detection ELISA.        Based on the in vivo data shown in FIGS. 27 and 28, and Table 18        below, M0161-B04 and M0171-A01 have been selected to be tested        head to head with M90-F11 and DX-2500 in Tg32B mice.

TABLE 18 Effect of affinity matured IgG and sol FAB in accelerating thehIgG Catabolism in Tg32B Mice: 5 & 20 mg/kg Intravenous Dose (Biotin IgG& Total IgG). % PBS control % PBS control of Biotin-IgG of total IgGremaining in the remaining in the serum at 168 hrs serum at 168 hrs 5mg/kg 20 mg/kg 5 mg/kg 20 mg/kg (1.7 mg/kg (6.7 mg/kg (1.7 mg/kg (6.7mg/kg IgGName sFab) sFab) sFab) sFab) Parent M90-F11 77 63 NA NA532A-M0171-A01 124 45 96 40 532A-M0171-A03 126 66 94 44 532A-M0159-A07131 59 96 40 532A-M0161-B04 100 41 76 24 532A-M171-A03- 182 103 140 108sFAb

Example 27 Effect of Anti-FcRn Antibodies on the Catabolism of hIgG

In vivo studies with anti-FcRn antibodies demonstrated efficacy indepleting circulating IgG. Dose dependent depletion was exhibited in twospecies, mice and monkeys, and by two routes of administration,intravenous and subcutaneous. In monkeys, reduction of IgG was notaccompanied by any change in circulating IgA, IgM or serum albumin.

A) Effect of Anti-FcRn Antibodies on the Catabolism of hIgG in Mice

Tg32B mice (mouse FcRn and mouse β2-macroglobulin knock-out)/knock-in(human FcRn and human β2-macroglobulin knock-in) were administered humanIgG at day 0. At day 1 and day 7 the mice were intravenouslyadministered different doses of the anti-FcRn antibodies M161-B04(DX-2504) and M171-A01. The level of human IgG in the serum of the micewas measured over 14 days. As shown in FIGS. 31A and 31B, the level ofhuman IgG was reduced significantly over the 14 day period for each ofthe antibodies administered. The decrease in IgG was dependent on theconcentration of anti-FcRn antibody administered.

B) Effect of Anti-FcRn Antibodies on the Catabolism of hIgG in Mice bySubcutaneous Administration.

Tg32B mice (mouse FcRn and mouse β2-macroglobulin knock-out)/knock-in(human FcRn and human (32-macroglobulin knock-in) were administeredhuman IgG at day 0. At day 1 and day 7 the mice were subcutaneouslyadministered different doses of the anti-FcRn antibody M161-B04(DX-2504). The level of human IgG in the serum of the mice was measuredover 14 days. As shown in FIG. 32, the level of human IgG was reducedsignificantly over the 14 day period for each of the antibodiesadministered. The decrease in IgG was dependent on the concentration ofanti-FcRn antibody administered. The efficacy of subcutaneousadministration is similar to intravenous administration.

C) Effect of Anti-FcRn Antibodies on the Catabolism of hIgG inCynomolgus Monkeys

Cynomolgus monkeys were administered different doses of the anti-FcRnantibody M161-B04 (DX-2504) and a vehicle control. FIG. 33A shows thetimeline of administration and FIG. 33B shows the results for thecontrol. The level of IgG in the serum of the monkeys was measured over14 days. As shown in FIGS. 34A, 34B, 35A, and 35B (individual monkeys)and FIG. 36 (group mean data), the level of IgG was reducedsignificantly over the 14 day period for each of the antibodiesadministered. The decrease in IgG was dependent on the concentration ofanti-FcRn antibody administered. The efficacy of subcutaneousadministration is similar to intravenous administration. FIGS. 37A-37Cshow that the serum levels of IgA, IgM and serum albumin are unaffectedby the administration of the anti-FcRn antibody.

The contents of all cited references including literature references,issued patents, published or non-published patent applications citedthroughout this application as well as those listed below are herebyexpressly incorporated by reference in their entireties. In case ofconflict, the present application, including any definitions herein,will control.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1-67. (canceled)
 68. A method of modulating an FcRn activity, the methodcomprising: contacting FcRn with an antibody that binds human FcRn,thereby modulating the activity of the FcRn, wherein the antibodycomprises a heavy chain (HC) immunoglobulin variable domain sequence anda light chain (LC) immunoglobulin variable domain sequence; and whereinthe HC comprises: a HC CDR1 comprising the amino acid sequence EYAMG(SEQ ID NO:144) or VYAMG (SEQ ID NO:156), a HC CDR2 comprising the aminoacid sequence SIGSSGGQTKYADSVKG (SEQ ID NO:145) or SIGSSGGPTKYADSVKG(SEQ ID NO:157), and a HC CDR3 comprising the amino acid sequenceLSTGELY (SEQ ID NO:146), LSIRELV (SEQ ID NO:158), LSIVDSY (SEQ IDNO:164), LSLGDSY (SEQ ID NO:170), or, LAIGDSY (SEQ ID NO:176); and theLC comprises: a LC CDR1 comprising the amino acid sequenceTGTGSDVGSYNLVS (SEQ ID NO:141), a LC CDR2 comprising the amino acidsequence GDSQRPS (SEQ ID NO:142), and a LC CDR3 comprising the aminoacid sequence CSYAGSGIYV (SEQ ID NO:143). 69-110. (canceled)
 111. Themethod of claim 68, wherein the FcRn is in a human subject.
 112. Themethod of claim 68, wherein the antibody prevents binding of the FcRn toan endogenous Ig.
 113. The method of claim 68, wherein the antibodyprevents binding of the FcRn to a therapeutic antibody.
 114. The methodof claim 68, wherein the binding between FcRn and the antibody occurs inan epithelial cell endosome.
 115. The method of claim 68, wherein thebinding between FcRn and the antibody occurs in an endothelial cellendosome.
 116. The method of claim 68, wherein the binding between FcRnand the antibody occurs on the cell surface.